I personally love them both, but the PMDG 737 is one of the most performant add-ons I have which I think is a marvel given how highly detailed it is. It really is optimized to an impressive level while still providing a beautiful cockpit. High res textures make everything sharp and readable and I find the sounds to be quite nice as well. I also recently added FS2Crew to complete the experience and I’m enjoying that as well.
Just my opinion.