Flyerndiver, this is just what I have found, and just my opinion:
EPDM and silicone will last longer than neoprene. To me, this is an advantage mostly with the hoses and mouthpiece valves. A good silicone duckbill would be great, but the silicone duckbills I have seen were WAY too flimsy for me. NOS mouthpieces have served me well, and last a long time. I have yet to wear one out. EPDM does have a bad taste, but neoprene tastes like the original hoses tasted back in the day, just as you can imagine by the smell of good, old neprene flippers and masks. You're not a vintage diver until you enjoy the smell and taste of neoprene! That said, my yellow hoses are silicone, and they perform perfectly. They are not too "soft" or flimsy compared to the neoprene hoses as far as I can tell.
As mentioned before, VDH sells a copy of the fine Mossback hookah port adapter. I have original Mossbacks which are no longer available, but the copies can get the job done too. I, also, can run an octopus and LP inflator off of this through a 3-way swivel when I dive with non-vintage divers who may need the octopus and/or feel uncomfortable with me filling my horsecollar manually
You can install a allen-keyed 3/8" plug when you don't need to run the extra gizmos, and it will look alot like an original hookah port cap to all but those in-the-know. Thus, you can retain the original look without ever having to remove the adapter. Also, you can attach a LP gauge there for testing/adjusting your IP whenever you want to. It's really handy!
As for band clamps vs. clips....I take the hoses off my reg after each day's diving and flush them and the regulator out with fresh water. If diving fresh water, I don't bother with the reg flush unless I can see that water somehow got into the cans. I tried a couple reproduction band clamps when they first came out, and the stainless hardware galled on me in short order and snapped off during disassembly. Aside from that setback, I was never able to get the cans tight enough to keep them from rotating in relation to one another, even after putting the recommended-at-the-time ugly crimps around the edges of the band. I was at a loss, as everyone was singing praises about the band clamp. Well, that was then, and this is now. Everyone is still singing band clamp praises, so I don't know if anything has really changed or not. They were originally stainless. Now I hear they are chrome plated steel, and I haven't heard of anyone having to bend them all up to get them to tighten anymore, so maybe they really are good now. Just relaying my experiences with trying them out a few years back, though I never trusted them for even one dive.
I decided to stick with the clips which were original to these rectangle label models back when they were sold anyway. I only tear into my regulators for servicing about once every two or three years anyway, and with a good daily flush have had no verdigris whatsoever inside. The VDH service kits are very nice and complete, and the prices are quite reasonable. To answer another of your questions, I found
original clips to be reuseable about 5-7 times (or so) before cracking. If you decide to stay with the original look of clips, I, or some other period diver can guide you with tips on how to r&r the clips. Once you know how, it isn't difficult at all.
Welcome to vintage diving! You are asking some good questions
P.S. You do not have to separate the cans to r&r duckbills.
P.P.S. Use a regular thickness banjo with a long yoke, or the Dacor tank valve with the built-in HP port to attach your gauge. If someone comes along trying to unload his "thin" banjo which "will work with your short yoke", beware. JMO, again!