I have a dry snorkel - haven't used it diving over my last 100 dives. When I used it, it seemed to twist whenever doing an entry from a boat, so always had to straighten it out before doing anything else. More importantly, to me, was that he hinge/plastic piece at the top of the snorkel as well as the mask clip took a beating - the mask clip doesn't attach as secure as it should, but I still use it for snorkeling.
You will learn what's best for you as you get more dives in. I've found that mostly doing boat dives, the snorkel is not saving any significant amount of air before the dive, and after the dive on the surface, I'm either okay with an inflated BC in calm water or I'm keeping the reg in my mouth if the water is a little choppy.
And now for a reason to keep a snorkel - on a trip to Aruba, I was exposed to several new experiences:
1. Most of he dives we did were my first drift dives
2. DM would dive with the divers for about 20 minutes and then leave to go back to the boat to pick you up where he thought you would come up.
3. On my 23rd dive ever, my buddy (a friend I still dive with today) and I were the only 2 divers and, per usual, were left after 20 minutes with the direction of keeping the reef on our right. The water had the least viz of any dive I'd done to that point (20-30 ft - my first 22 dives were all pretty good.) We were still rookies having done 12 dives together prior to this dive. As we were nearing the end of the dive, I knew I was running very low on air but still had enough as we swam at about 15-20 feet for our safety stop before surfacing. As we surfaced I had nothing in the tank and the boat wasn't near us. I honestly don't remember if I used the snorkel or just floated waiting for a pickup. Maybe a little of both.