I guess it's just all about personal preference, I sided with an 8x57jrs Express because it was legal all across Europe, but since a change in laws I mainly use 30-06, probably a bigger calibre would have more stopping power, but if you shoot driven game as I do, when it can be Red, Sika, Moufflon, Boar and sometimes Roe, I prefer these calibres, but that's my personal preference, even a 9.3 or 300 win won't stop a boar in the wrong place, many French hunters have turned to 30-06 since the law changes.