Having to start over?

from what I understand the prinbot simple uses  fishing line to to move the axis if the drive pulley slips you lose steps. the soliddoodle uses timing belts for the xy and a screw for the z. a regular screw a better method would be an acme screw or even better a ball screw. so from that perspective IMHO much less likely to mess up.

That said no manufacturing process no machine will produce perfect parts every time. or even usable parts every time. every tool is only as good as the operator. the Hollywood iron man fantasy of computer make me this part and a part pops out is total BS. remember the old adage garbage in garbage out this applies to 3d printing.  there are hundreds of variables to control.  first the part must be designed properly. the part must be oriented properly. the machine must be adjusted and maintained. the program settings have to be set correctly.   
I have a buddy who is an engineer he has worked as an engineer and as an educator he is experienced with high end stratasys  3-d printers. His advice to me is you can not ell the printer what you want  you need to figure out what it thinks it wants and do that. Let it teach you.

do not think you can push a button and a part comes out. operating a 3d printer you are operating a cnc machine. it is an additive machine not a mill, lathe or grinder but it is still cnc. but there is more. you are also the programmer the designer, the purchasing agent the setup man the mechanic that fixes the machine, the engineer and the janitor.

if you expect to get everything right the first time and  make a dozen parts you are barking up the wrong tree. You need to look at 3-d printing like a college engineering lab. you need to read learn and study then you apply what you learned and then the the machine will show you what you still need to learn. expect to make a few practice pieces before you get it right
then when you get it right something will change and you learn some more.
In the early days of automobiles they needed a lot of tinkering and fixing. They were not always reliable.
Home shop level 3-d printing is relatively new. It is amazing but still needs lots of human input and the human still needs to think and serve the needs of the machine to get what the human wants out of it.
Tin

From a slightly less abstract perspective:

It takes a relatively small amount of time to calibrate a SD properly. Once done, you should be able to avoid another calibration for months. I would still suggest monthly maintenance (clean, regrease, etc). What causes a pre-mature need for calibration is a crash or bump. The bed sits on top relatively long screws tensioned by springs. They wobble. If the printhead hits a curling edge, there is a chance this will knock the bed out of place from your last calibration, and things have to get calibrated again.

The real question here is what causes the bump in the first place. If you have alot of overhangs, or print solid objects that have no purposed voids to relieve the tension when it cools, and you do not have a gcode fan on your printhead then you are limited to what can be printed without causing a crash. This goes for any printer. Ask too much from the printer, something goes wrong. It is not a direct fault of the hardware. It takes a lot of practice to figure out what your printer is capable of and what it is capable of.

I understand that every printer will have problems during a print here and there, but I'm wanting something that can complete a print 95% of the time. The printrbot would take about 3 failed prints for every 1 good print. That's what I meant by getting frustrated with it.

+1 this seems like the answer you don't want to hear.  Pay close attention to your original post, re-read it a couple of times (I have). All of the things that you find frustrating will exist at some level with all FDM printers.
So if your real question is can you print reliably 95% of the time with an SD?
Well.... Myself, Adrian and Hazer can along with many others that have the knowledge and desire to learn, tinker and the understanding to make an FDM printer work.  So I guess it is up to you.

Sold them in frustration ? lol

(I;m being a tad cynical.. but only a tad..... there is a fair few people on this forum that dumped and ran )

Guess again.... The type of line that is being used (digital braid synthetic) was not originally developed as fishing line.  I have been slamming a Bulldog XL around for quite a while now at speeds and acceleration numbers beyond what most would think possible.  I can assure you if installed properly it will not slip even a little.  In fact myself and several others would consider it a serious upgrade.

Yeah...

Observation... I know its easy to get excited in this hobby... But its important to slow down and pump the brakes before launching in with difinitive statements on subjects.

well I know from fishing with all types line, equipment. Braided eats up anything it rubs on as its very abrasive. it will eat through any material used as guide eyes long b4 the line needs replaced so likely it does that to the spools on printers. I have been using my SD2 for over 18 months now. (wish I had this kind of feedback b4 buying a 3D printer). but all these guys are right. I have been frustrated to the point many would have tossed the printer out in traffic just to watch it get beat to pieces LOL. but after sticking to it (some times 247 for many days) and help from others like on here (cant say much for factory tech support anywhere) I have weeks when my salable prints do maybe better than 90% then days when nobody wants to get within ear shot of my printing room for the fits it gives me just to get 1 good print for my 3Dhub site. like I told my wife and son yesterday. "these 3D printers are amazing 'when they work right' but trash when they dont" ;^P

1 thing I do is only single prints, not multi items at same time as if ya have to kill print job for any reason you only loose the 1 partial item not 8. and loss comes out of your pocket/profits. I had to adjust my costs on 3D hubs for this and the fact they do the calculating based on zero support material and only 20% infill like powder printers do. also setup fee includes if ya have to swap filament types/color which costs filament purging head too. most owners of these printers use them for items they been making with other methods or couldnt do with other methods. resale just helps recoup some investment.

wish I could get somebody to solder connections on my board for cooling fans for left side motor and at extruder tip for bridges. I made parts for them and have fans.
the new board has micro SD slot too for better flow of G-code without skipping while doing other stuff on puter. I use laptop but gonna update battery in my UPS for printer so power fails wont loose print for at least an hour.

anyway like others said if your good at things they said and can stay with it to see things through. if 6x6x6 inches is big enough for your prints the SD2 will be best choice for 3D printer type under $10,000 where powder type start. or under $1-3K for this type.

I'm not sure I understand the question... If your asking how it stays indexed?  I would answer with another question.  Why would it need to be indexed?  If it doesn't slip (which it doesn't) and it starts at zero, so long as the steps per mm are calibrated it doesn't matter.  My thought is you should try it and see for yourself.