Both are great cartridges and have accounted for many a deer - Personally I would go for the 6.5 Swede simply because it will push heavier bullets.
If your rifle doesnt like 100gn pills in .243 then you suddenly cant use it in Scotland on reds because 100gn is the max for .243 and the minimum for reds north of the border. You can get up to (I think) 156gn with the Swede so you have a lot more choice of legal loads.
If your rifle doesnt like 100gn pills in .243 then you suddenly cant use it in Scotland on reds because 100gn is the max for .243 and the minimum for reds north of the border. You can get up to (I think) 156gn with the Swede so you have a lot more choice of legal loads.