I believe one of the major development forces behind the modular system was LE sales. Many agencies, particularly in the northeast, only issue one type of gun and do not allow officers to use personally owned weapons on duty. There is reasoning behind this (that I don't necessarily agree with); one type of ammo to stock, dept. armorer only needs to go to one school, ability to interchange magazines in a major firefight. However, not every officer has the same size hands and one size gun does not fit all.
With the 250, agencies could have officers shoot all three frame sizes and determine which is most comfortable and which they are most proficient with. AFAIK, all three sizes have the same size magwell, so mags would be interchangeable, and the receiver is the same, so the dept. armorer would always be working with the same system. The price is also much more attractive than their 226/229 line...our agency price on 229s is close to RETAIL for a 250.
Unfortunately they (so far) only offer it with their atrocious DAO trigger, and not their much-superior DAK or even the DA/SA.
I put around 100 rounds through one at a rental range and was not very impressed. It felt cheap, didn't feel right in my hand at all, and I shot much worse with it than I do my 229 DAK. It's also ugly, but that isn't a factor in anything other than safe queens.