350cc in mod plus will be much wider than 350 in HP. What’s your BWD? You want to choose an implant probably no less than 1cm smaller or 1cm wider. Wider = wide boob and cleavage, but go too wide and you risk uni boob (symmastasia).
Most make their choices based on this.
I went mod+ as wanted to fill my BWD but didn’t want loads of projection. Read some of my other posts if you want any more info.