Your Poulan oil is likely a 40:1 mix which will work in the Stihl. I prefer (and Stihl recommends) a 50:1 mix to keep carbon deposits and smoke to a minimum.
Oil to run both? My experience is that Poulan should be fine with a quality 50:1 oil like Stihl HP Ultra (a very good synthetic oil). Other options are even leaner, Opti2 and Amsoil Saber Professional, both mix at 100:1 (80:1 if you get every last drop out of the package,
). I am currently running the Saber Pro in all of my 2-cycle equipment with zero issues. (FWIW: My equipment is all Stihl spec'd at 50:1 except the 031 and my HF 2-cycle generator.) Going to do the crank seals on my 034 soon so I will pull the muffler and check for scoring/scuffing. That cylinder/piston was perfect prior to the switch in oils.
Side Note: I run my HF genny on 50:1 currently as it is still on it's 2nd tank of fuel. I started it up new on the 100:1 Amsoil and wasn't happy with how hot things were getting. I'm guessing the machine work is a little rough on that one and the fit may be a bit tight yet as well. I will try going back to 100:1 after I've run a couple more tanks through it. My brand new SH86 (Stihl) ran 3-4 tanks of 100:1 through it with no issues.