I have owned both the Studio 60V2 and the LSi-15. Up front the Polks are much better speakers IMO. Bass is the only area where the Paradigms beat the Polks. In every other category, the LSi-15s excel. The tweeter Polk uses is phenomenal for the money, especially at used price, while the Paradigm tweeter is somewhat fatiguing. For reference, I've also owned Vandersteen 2CE Signatures, Meadowlark Audio Shearwater Hot Rods, Eminent Technology LFT-8As, as well as a few well respected monitors, and the Polks are the best sounding speakers I've owned.
I'm sure there are many suggestions but if it's between the two mentioned, go for the Polks.