It's personal preference. I see the appeal of the 43x, but the 48 is a bit more appealing for me. Plus I could remove the 48 slide and put a 43x slide on there if I chose to do that. I am uncertain if the funky 48 upper will go on a 43x frame... Being a long time 19 carrier, I suppose the 48 just seems right. Either one will be a great carry gun.
48, 43x, and 43 slides will fit and function 100% on all 48, 43x, 43 frames. If you put a 48 slide on a 43x frame, you have exactly a 48. The frame of the 48 and 43x are identical. Put a 43 slide on a 48 frame and you have a 43x. You can also put a 48 slide on a 43 frame, works fine. If you want all 3 guns your best bet is to buy a 48 and 43. You can mix and match to create your own 43x