I had a similar decision to make.
First off, it is unlikely you would damage your speakers even with the more powerful module. Most speakers get "blown" when sending distortion to the speakers and most speakers can handle fairly large transients of a clean signal. In other words, even though the amp is capable of much more power than your speakers are rated for, you would probably only damage them by turning it up so ridiculously loud it would sound awful.
The sensitivity of your B&Ws is 88dB, which is about average. More power is almost always better for headroom reasons - reason being amps work best when not pushed hard into distortion (ie the knee on Amir's graphs). However, here we have measurements and these amps can go pretty far into their power output before any distotion occurs, so if you always listen at moderate levels the 122 would be fine as you know you can get 75 watts (ish) without distortion.
Conventional wisdom is to get more power to cover all future scenarios - the times you want to play really loud, or the option to get less sensitive speakers in the future. As the 252 is not that much more $, that's probably the best choice in most cases.
For me, I made a conscious, considered choice for the 122 and less power - which goes against nearly everything I have ever thought about building a system.
My reasons:
- My system has two powered subs, so I find I don't listen as loud as I used to, as the full sonic spectrum - including full bass impact - is present, even at lower volume levels
- My current amp is only rated at 60 watts/ch and I never turn it up past 10:00 now
- My listening room is narrow, so listening position is only about 7 ft from the speakers
- At the time, I as considering the SMSL ML500, which XLR outputs were measured as "hot" by Amir (well above 4v standard). Since decided on Topping DX7PRO though
So, considering all of the above, I concluded that the 122 was more than enough power for me, and I wanted more "play" in the volume dial to make more precise volume adjustments.
In summary, it's almost always a good idea to choose more power, and only in specific situations (like mine) does it make sense to choose less power.