It's a toss-up. 48's advantage: Longer barrel, more weight in front for recoil absorption. Longer sight picture. 43x's advantage. Easier to carry IWB for some. Partial equalizer: A TLR-6 softens the felt recoil. With the right replacement sights you can lengthen the sight picture of the 43x.
I'm 5'9" and would not like the extra inch of a 48 stuck down the front of my pants in AIWB. Seated would be really uncomfortable. 43x is just short enough for me but long enough to do the job. However some folks feel that the 48 prevents "flop" (something I've not experienced with a 43x). Most folks who have shot both find there is little difference between the two in terms of accuracy and shot placement. But again, a naked 48, again, will reduce felt recoil. With S15 mags the 48 could be a great alternative to a G19.