We don’t officially support Squeezelite (but many people have found that it works fine).
Sync quality is much better with RAAT (both in terms of tightness of sync and the disruptiveness of the mechanism used to correct for clock drift). Roon+RAAT linking is probably always going to be better than Squeezebox because the underlying design of RAAT’s zone linking system takes into account over a decade of progress that has happened since SlimDevices designed their technique. And, of course, we focus more effort+attention on RAAT than Squeezebox internally.
Roon+RAAT can support more/higher-res formats in a bit-perfect manner than Roon+Squeezelite. This is not relevant unless you actually have content in those formats.
I don’t know how Squeezelite volume control works, but we have a few different options including a nice noise-shaped dithered volume control + a mechanism for passing volume commands onto a USB device. If you are planning on controlling volume from Roon, this may make a substantive difference.