Hello ,I had the same dilemma a few months ago when deciding to apply for my 1st deer calibre ( i only shot rimmies & shotgun before ),so i applied for a .243 & .308 but after shooting these calibres on the range plus various others I really liked the 6.5 x 55,it just shoots smoothly with very little recoil ( its more like a push than a kick ! ) so you keep youre sight picture when firing,then i did a stalk with john robson and used his Sako in 6.5 and got my 1st deer.
By the time I had my feo home visit i just wanted the 6.5 and asked her if i could change my variation and she said yes but you can only have one calibre as its my 1st centrefire,this suited me fine and when you think about it in terms of bullet size and weights the 6.5 is in between .243 & .308 and is legal for all deer species,goat & even boar ! BUT
if i was shooting boar i would prefer to use something in the 30 cal range.
I hope this has helped or has it just muddied the waters further,lee