I would think that either one would be fine out to 500 yards. I have a 25-06 and have made a few kill shots out to 430 yards. I would say the the 25 would be a little flatter shooting than the 30 but the 30 will hit harder when it gets there. The 30-06 has such a wide variety of loads though that you could have a very good round at those distances. Thats a long way to be shooting at a deer. My shots have been on javelina and coyotes. I would say that with either caliber I would count more on shooter ability and confidence in making the shot over the actual load itself. If you are confident in your ability to hit your mark then I would say either would be just fine. I dont know if I would want to chance a shot at a deer past 500 yards though but that is just my opinion. I did let a 9 point with a 3 inch drop tine go because I wasnt confident in my ability at about 480 yards.