For me its a case of using what I have which is mainly 6mm or 6.5 (260 rem) definitely noting the previous comments re splash observation.
I am not a big bloke so weigh IS an issue for me in terms of manoeuvrability in barricades etc rather than simple carry weight.
When I add bags to an already heavy rig I struggle and as most positions are supported in some way I see weight as a disadvantage..... within sensible limits of course.
If I could get a new and dedicated rig built it would be 6.5mm flavour, shortish (max 24") carbon barrel ex Josh (would need to check adequate ballistics at range), 139/140g bullet and a stock offering minimal snag surfaces.