OK, I'm a noob but from my understnading: The scale (length of the fingerboard and nut to saddle) is longer, so the strings are tighter. The concerts generally use the same strings as sopranos. My sopranos are mostly softer tension compared to all my concerts (all two, LOL!) except one soprano that has Ko'olau Golds on it, which I found out later are high tension, and I can really feel it, they fret more like my tenor. They will be replaced soon, I think they are sort of strangling the uke's voice too.
Strings do make a difference too, a lighter tension (thickness) string on a tenor can make a big difference in how it feels and how hard it is to fret. Different materials the strings are made from also affect feel, sound level and response of the instrument. I think it might be safe to say strings can literally make or break a uke.
I agree with Link, any excuse to have more ukes, like one of each size to start, then two of each size so you can have some re-entrant, some low 4th, or in the case of sopranos different tunings, then also factor in different woods = mahogany, koa, mango, spruce top, cedar top, etc., that's like 18 minimum....