As much as I think more small-plane time is valuable, I find it hard to believe that those extra 50hrs multi is going to get you through your first 121 training event.
Seriously - how much did you learn in 50 hours of time-building w/only the Airlines in mind? I'm sure ya'll know your learning plateaus long before then with your first 500 hrs or so of SE.
At TSA, half my class washed-out of training. EVERY one of those guys had two or three times the TT and Multi I had logged. Certainly not trying to toot my own horn, but telling newbies to go out and spend another 10K on multi-time because it'll make them a better pilot is at best a STRETCH of the truth. I know I certainly learned boat-loads more about "Jet Judgement" in my 25 hrs of IOE than in my 75 of bought Multi-time.
A guy that can make it through 121 training with 100hrs multi can also make it through at 50 if they put their heads to it. Most guys have it, a few don't - regardless of the TT in their logbooks!