I prefer 6.5x47 Lapua in a bolt gun here is why.
6.5x47 Lapua gets same velocity with less powder in a cartridge that uses small rifle primers and last over twice as long as the 6.5 creed more. The Lapua brass is cheaper and the 6.5x47 fits the mags better with long bullets. As far as gun chiose most matches give you plenty of time to cycle a bolt and you do lots of barrier shooting. If you have a nice trigger around 2-3lbs in a gas gun you will have to train yourself not to bump fire it on accident. Doing that at a match would be bad.
with a bolt gun you can neck size your brass if you want and it is easier to clear a hang up or feeding issue. If your gas gun jams you most likely are out of time by the time you fix it. Shooting a good group is one thing but consistency is another and it is my opinion that a bolt gun gives you the highest chance to consistently repeat accurate shooting. A solid trued, free floted,smooth manual operation with fire formed brass. That's my opinion.