Been meaning to get some mechs from both Mecha Front and Precinct Omega. They look great. Judging by photos, they don’t strike me as having more difficult-to-reach areas than a typical Dream Pod 9 mech, so I’m fairly sure I’m going to assemble them before painting.
All this is just personal preference, of course. I value being able to paint highlighting and shading in the right places, more than I value ease of access with a brush. Also I don’t want glue getting on top of the paint. I probably have a high tolerance level for putting up with painting hard-to-reach areas on figures.