I'm not up on all the weight differences but have two buddies with the sx4 24" guns, they seem lighter than my sx3 and shoulder very well. If I was in the market I would handle one before buying anything else.
I think it all comes down to what feels right for you. There's a lot of nice 20 autos out now that will perform and pattern very well. Just decide on budget and get yours hands on a few to compare before buying.
