It really boils down to simple SPL & volume of air moved. I like 12's and am not a fan of 10's so I am biased. A pair of Rumble 210's is going to give you more of each than a pair of 112's. Larger diameter drivers have broader dispersion and usually a smoother midrange. This is especially true of the custom Eminence designed ceramic-ferrite 15's for Fender Rumbles. A pair of 115's will move as much air as 4x10's. There's your BIG SPL picture. Tone wise it really comes down to your ear and what you like best. In my experience of critical listening, there isn't a tremendous difference in frequency response or initial quickness of response.
As far as your sharp pick attack goes, you just have to seek your balance in rolling off your tone control and back off your amp's treble until your attack equals your midrange meat and bottom punch. That's what they're for.
I also was turned off to 10s. but then I heard the Rumble 500 combo. IMO they sound leagues better than most other 210 cabs. the speakers the main reason I bought the combo.
I've played around in a store with a Rumble 200/15, I think it sounds similar to the 210, which is kind of a turnoff to me as I was hoping it would have more barky midrange.
Back when I was first figuring out what I wanted from the Rumble, I had a 500 combo (still do) and an ext 210 cab. I thought the low end was too much. Therefore, this might be what you want to look at. The stack looks good and is crazy loud for what it s. An excellent rock setup. But I landed on the two 112 cabs specifically because I wanted more midrange and less bass. While the 112 cab is definitely a more low-end-ish 112, I'm not sure it's the best for that "rounded" sound. But might be...
To my ear, the Rumble "sound" doesn't have the "rounded" sound that amps like Ampeg does. Which is why the Rumbles sound better! I think if i was after the warm round sound I'd start at the Rumble head, by engaging the vintage switch, and turning off the tweeter. You might want to add bass from there, but be forewarned that the Vintage switch already pushes the low end a good bit and it might be damaging to a speaker when adding even more low end to that. Just be careful.
One other angle to that rounded sound is to use a low pass filter - Josh Broughton on here as Azure Skies makes one that's killer. It's the best way I know of to round off the top end of any bass or amp, without even turning off the tweeter. Just start turning down the high end and it progressively removes all frequencies above the threshold, down to something like 200 hz.