There are several ways to look at this. One way is to say I can go larger in the rear and now turn that corner and climb that hill in 3rd where before I had to use 2nd. OR, you can go smaller on the rear and turn that corner and climb the hill in 2nd, but go faster than you did before.
In general though, I'd agree with big Yac, lower the ratio for woods riding. If you go smaller on the front, make sure that the angle the chain leaves the front plastic guide isn't increased so much that it causes pre-mature wear. Same with going larger on the rear. Make sure that the larger sprocket doesn't put to much down force on the rear chain guide causing pre-mature wear. Most bigger bikes handle the rear sprocket changes pretty well.
Yac made another good point about getting home. Sometimes you pop out on the logging road, and want to beat feet. Nice to make a quick sprocket change and fly on home. All depends on how far it is back to the truck.
One trick I've used on chains lengths is to cut my chain in two places (two master links), and carry to different length sections, one for the bigger sprocket, and one for the smaller. I cut the chain such that I never have more than one master link on the drive side at a given time. I've used this concept more for racing than woods riding, but the same principle would apply.
If you don't want to do the math, the rule of thumb is dropping one tooth count in the front is close to adding 3 in the rear. However, with larger sprockets in the rear, it's closer to adding 4 in the rear to drop one in the front.
50/14 = 3.571
54/14 = 3.857
50/13 = 3.846
Best of luck
