IMO, find the money to buy the three tins. What will measuring the bore size tell you? Sure, generally, pellets that fit snugly tend to shoot better than those that bounce off the lands flying down the bore, but there are always exceptions, and who knows what the pellet size will be after the spring-piston air whacks it in the skirt, or if in the end the Baracuda Match of any size will shoot better than any other pellet you can get. Testing is the only sure way to find out.
You can always use up the pellets you don't like in practice (if you can get the losers to group better, then you'll really do well with the favorite pellet), or trade them with a friend.