I have the same dilemma. With my Guardsmen I would glue the left arm but leave the lasgun (right) arm off so I could paint the chest beneath, always worked fine for me.
HOWEVER...
...I recently read/watched something about various painting techniques (can't remember exactly what or where it was) and realised that painting in such a way sometimes creates complications with the highlights and shading etc. depending on how swish and realistic you want your results to be.
As an example if you leave the arms off, you can get at the chest and the armpits to paint them all the way up to a highlight stage i.e. they get full-light exposure. However when you whack the arms on, these areas are then covered and so in reality would be shaded and should maybe be left as the darker/midtone instead...
It's a bit 'high brow' admittedly, I was always happy with the results on my IG so it's currently a toss up for what I'll do on my Empire guys.

Arms off = easier for painting.
Arms on = more realistic in terms of shading results.