This thread quickly became TLDR. So if someone else already said it, I'm going to say it again. Your 3x will likely have a lower low gear ratio than most any 2x bikes if we are talking common and in general. And very likely the same high ratio gearing. So really, IMO, your main consideration is if you need the low ratios you currently get.
Gear ratios are front teeth divided by back teeth. (on the bike, not in mouth) So they are easy to figure out.