Despite the overall positive reviews of the L-frame, I WOULD worry somewhat about excessive magnums in L-frames. I've seen some develop timing problems with low magnum round counts, especially if "hot" magnum loads are used. My own personal L-frame (686) developed binding and timing problems after a few thousand relatively hot .357 magnum rounds.
The N frame, OTOH, should be perfectly fine to shoot magnums in all day IMO.