It might say something about the Hoplite's capabilities that a few decades later the League procured an upgraded version of the Sentinel to do the same infantry support job.
The Sentinel manages to be worse overall though, unless we are talking about the Royal version. But even then, frankly the 4B is better for infantry support, as it has direct fire and indirect fire capabilities and is tougher. The Sentinel is faster and lighter to be sure, but not sure those are terribly relevant here.
The real reason for the Sentinel acquisition seems to be that it was exclusive to the Lyran Commonwealth. So the SLDF wanted it as well, and they wanted an upgraded version while at it. (SNT-1S was the original Lyran exclusive model.)
EDIT Looks like the Sentinel fluff indicates it is used for forward observer duties, or as a commander's ride. So it does pull double duty as fire support and recon 'Mech, something the Hoplite isn't good at really.
I'm amazed that this rather unremarkable Mech's kicked up such an interesting debate and thread :D
Actually this makes sense. There is little to be said about good 'Mechs with clear purpose they can do effectively. Everyone is like "it is good", and add either "i like it" or "i don't care for it (because it is good)" usually, and that's all there's to be said.
But oddballs like this, yeah, there's stuff to be wondered and talked about.