What Diaper Closure is Best for Me?
SNAPS vs VELCRO vs SNAPPIS or PINS
As for closures systems, I myself, through years of personal use, have come to prefer snaps - while they may somewhat limit the adjustability, they are more attractive (in my opinion) and remain so over time, as well as maintain their functionality darn near forever. The other downside is that they are 'slightly' harder to put on a wiggly baby. This isn't a problem for someone who changes babies often, but for a parent who rarely does or grandparents/babysitters this might be a complaint.
Velcro is quick, easy to use, and infinately adjustable, but it WILL wear out. If you are very careful about attaching it to the laundry fold-back tabs prior to washing so it doesn't hang up in the wash, clean out the hook side frequently, and don't get too rough with it, it might last you 2 years, but it will wear out before the cover does, and under normal use conditions will wear out after about 12-18 months and will need to be replaced. Fortunately this is fairly easy to do for even novice seamstresses, but you would want a sewing machine.
Snappis provide the infinate adjustability of velcro and the added bonus of making your cover reversible. They can also make your cover fit a wider range as you can literally make it as small as you want for tiny newborns. However, they will pull any fabric over time. These are better on woven wools or tightly knit/dense wools than bulky loose ones, and you can reduce wear and tear by NOT pulling the snappi to the absolute tightest it will go, just get a "just snug" fit...
And lastly, old-fashioned diaper pins or even large safety pins provide many of the benefits of snappis while being inexpensive and readily available and also reducing wear and tear on your diapers - however there is always the "poke" factor - scary for both you and your babybear if you are not confident with them, are sleep-deprived (what mom isn't?) or just clumsy like me.
Really it is purely a matter of personal preference which you choose. Many people swear by one type of closure or another (some even swear by pins!) that's why I offer you a choice. I hope this helps.