why would one pla stick and a second pla curl and float - shrink charactoristics ??

I ordered two different pla spools, one a generic spool and the second a name brand. The generic came first and I tested it 3 times trying to print a 2 1/2 x 3 1/2 box on a raft. I tried to adjust the bed an nozzle between each test. Each time first the raft curled and then the box on the corners. After a couple of hours when the printer would return to one of the liftet corners the nozzle would grab the entire print and pull it off the bed.
When the name brand arrived I tested it using the final setting from the last generic test. I first printed the box and then the cover. Each time the raft stuck to the bed and the box / cover to the raft. If anything the adhesion was too strong, it was difficult to remove.
My speculation is the generic PLA is shrinking more then the name brand.
My questions are:
1. Is this a common observation. Is it normal for different PLA to have different shrinking charactoristics?
2. Beyond trial and error is there a way to tell before purchase how a PLA will behave?
3. Is it as simple as find a brand and stick with it?
Thanks, Dan

No telling really. It could have been a color additive. It could have been contaminated with ABS or other plastic. Pure PLA (clear, no color) can deform as well, although it tends to start well and delaminate further up.

This is why people play around with heated beds and glue stick etc, to get good bed adhesion. And pay more for consistent filament.

I just went through this, too. I have a spool of no-name PLA that is several years old. It will stick to nothing, including itself. I tried nozzle temps from 180-225. Bed temps from 20-100. Glue stick, painters tape, bare bed. Dried the spool in the oven. Nothing worked. The print lifts, curls, cracks between layers. The filament itself feels OK, and isn't brittle, but has absolutely no odor when printed.

A fresh spool of PLA Pro from Matterhackers prints great at any reasonable temp, and has that typical "fruity" smell when printing.

Both spools were white. Pick a good name brand and stick to it.