What's the best SLA resin out there today?

No DLP resin will not work on a Formlabs printer. The resins are formulated differently due to the difference in the laser wattage versus the uv array wattage. Like wise Laser formulated resins will not work in DLP systems. Whatever resin you choose you need to make sure it is formulated for a laser based SLA process.

Thanks for the answer. I really appreciate that. So Carl, I'm sure there have been a lot of threads on this subject but none recently that I can find: What's your thoughts on third party resin for the form one? Shoud I pay the extra money for the FormLabs resin or is there a viable alternative?

If you mean me, I use ApplyLabWorks just like skiprmike, but I have no issues with it.  In fact, I think that all current Formlabs resins are formulated and tweaked for the Form 2, and don't really work as well in the Form 1+.

I, for one,  really like the ALW resin, and for the past year and a half been using it almost exclusively.  I've tried a variety of ALW resins, and the only one I didn't care for was the flexible.  I currently use their beige/white and gray, and the only resin I still use from FormLabs is clear, since ALW doesn't yet have a clear.

@skiprmike.  What is it exactly about the ALW resin that you don't think is as good as FormLabs, or contrarily, what is it about FormLabs that makes it better than ALW?  I can see if you were using a specialty type resin like castable or similar, but most of those don't work in the Form 1 to start with. 

Anyway, there are quite a few aftermarket resins, which have been used with various degrees of success in Formlabs printers.  I suggest you head over to the FormLabs Forums and browse through there if you're looking for alternatives.

There's a couple of reasons. 

The Form 2 has a different laser, more powerful, and as such they can formulate certain resins to work with that.  If used with the Form 1, they wouldn't be able to cure correctly.  Also the peel mechanism, and the peel strategies programmed for some of these resins only work on the Form 2, because it works differently.

Additionally, some resins react so strongly with the PDMS coating in the tank, they would kill the coating in only a few passes, so they reserved these resins for their newer tank LT, which seems to be using a combination of PDMS with FEP on top of it.  This surface seems to be much more resilient to the "harsher" resin formulations.  However, they don't make the LT tank for the Form 1/1+, only the Form 2.

Last but not least, because that's FormLabs way of forcing users to move on to the next model.  As new resins were developed, they were are only available as selectable options if you have the Form 2.

The Form 1/1+ is a "dead & buried" system as far as FormLabs is concerned, and they are doing everything in their power to make it go away.  Consumables are going away, you can't buy tanks any longer, repair parts are gone, so if your printer breaks down, you're SOL.  Most of their resins, even though they claim some are still compatible with the Form 1, have already been tweaked for the Form 2 and don't print as well on the older printers, and so on.

It's for this reason, those of us that still have functioning Form 1's are looking at, and supporting those 3rd party vendors, because they represent the last resources for this printer.