This is THE age old debate over which gun to use and hopefully, as this is part of everyones peception and contribution to the knowledge base, will never end. I agree with Staggie that Sika are really hard to kill, the buggers never seem to know when they are dead, then they pull stunts like dropping down and creeping off, real tough and crafty and as twitchy as can be. Having said that I do use my 243 on Sika hinds, I know the gun and have confidence in my ability to use it on the hinds. I can't speak about the 308's game taking ability as I have only ever killed paper with one. If I am going out specifically for stag's then it is my 6.5X55, for me that is perfect.
Then again I know people up here in the Highlands who have used a 243 on everything for 30 plus years. So who is right and who is wrong I don't know but, the good news is that everyone seem's to be thinking about the game first when deciding on a calibre to use, which can only be good.
John