I have played or am playing with the following (all strung with a Kilppermate drop weight stringer):
Pro Line Evolution - LOVE this string. Currently have it in a Head TGK 238.2 (16x19), Head TGK 238.1 (18x20) and a stock Prestige Pro at 56lbs and it feels great. Ball pocketing is good and the strings do not move around a lot. Has good feel even at higher tensions. I have had it as high as 62lbs and it still has good feel to the strings. I would recommend this string HANDS DOWN to anyone looking for a poly that is arm friendly. I have three fellow players on my league team using/loving this string right now.
Pro-Line II - have used as both a full bed of 18g and have used the 18g as a hybrid with Multifibre as the crosses. GREAT poly. Does not break quickly and maintains tension well. Ok to use at higher (60+ lbs) tensions. Used 17g for a while, but I prefer the 18g as it has a little more pop. Seems like the black has a little bit more pop than the red, but that could be my imagination.
Helix - did not care for this string. Has to be strung below 55lbs or it breaks very quickly. At 54lbs in a MG Radical MP it felt like a trampoline. Strung a MG Radical MP @ 60lbs at it broke before hitting a ball.
Pro-Line X - same as above. Strung this at 58lbs in a stock Prestige Pro and it didn't last a set.
Multifibre - have used as a full bed and as a hybrid with PLII. AWESOME multi for a reasonable price. Would put it right behind a TF X-one or a NRG2. Good feel, good tension maintenance and it lasts a long time even when frayed. If you are looking for an affordable, arm-friendly multi, this is the way to go.
Super Smash Orange - very firm poly. I liked the string response, but my elbow and shoulder did not. Have it presently in a MG Radical MP at 58lbs. May try to drop this one down to around 54lbs to see what it feels like.
Hybrix Spin - great combo of a firm, textured main and a soft multi cross. I have had this one strung as high as 64lbs in a Prince TT Air Rip and it takes forever to break. Crosses will go before the mains. Good feeling string with a fair amount of spin available coming off the string bed. Mains are similar to PLI and crosses are basically Multifibre. Not sure if you can even buy this one anymore. Used this string for a while before switching to the PLII/Multifibre hybrid and now the PL Evo.
Spiky Shark - great spin producing string out of the gate, but it seems to lose its texture rather quickly. I did up a hybrid with SS in the mains and PLII 18g in the crosses, both at 58lbs. Was great for about four sets, then felt like it went dead.
Hope this helps!
3 x Head TGK 238.1, 5 x TGK 238.2, 1 x TGK 238.4, 2 x TGK 260.2