It depends on intended use, of course. The choice for me depends more on weight than caliber. Mediums like .400/.350 and .400/.360 work perfectly for the range of game that a .275 or .303 double would be suitable for, and then some. Also, too many small bore and medium doubles are as heavy as a typical rifle in the .450/.400 to .470 group.
The .360 No. 2 is wonderful. However, excepting the rare "lightweight" models, the rifles are dependably 10-10.5 lbs. Likewise most .333s and WR .318 rimless. Hell with that!
Some of the small bores are just as bad. Recently saw a nice .280 Flanged - 10.5 lbs without scope. Quite a few .303s were built at a nice weight of 8 lbs or so, but some were 9lbs, heavier than my .400/.360.
Nothing wrong with the small bore doubles, as long as they are built to an appropriate weight, likewise the mediums. -----------------------------------------------------
-------------------- "Serious rifles have two barrels, everything else just burns gunpowder."