Hi Brutus! My husband and I have been diving with full face masks for over 10 years now, and we absolutely love them! The safety factor alone is worth the price of admission (although admittedly, it is a bit steep). We have AGA masks, with Buddyphone communications. They have been very reliable, with proper maintainance of course. We dive South Pacific whenever we can, and in clear water with no major rock outcroppings, I would say we have a good, clear range of 150 feet. Locally at Catalina Island, off the Southern California coast, with a lot of kelp and rocks between us, we might get as little as 50-60 foot audible range, but I would say the average is still more like 100 ft. The clarity of the transmissions is surprisingly good in most cases, very little garble. You do have to get used to them, and learn to listen and talk a little differently than you do on land, naturally, but we found that comes almost instinctively after just a few dives.
I'm not sure what the Neptune masks use for clearing your ears, I assume they have a rubber piece you push up against your nostrils? That's how ours work, and again in just a few dives, you'll find it comes naturally. For myself, I can't say that it made it any for better or worse for clearing my ears. I always have had some trouble with my ears on a multi-day dive trip and I still do. But we also dive with another couple who have the same masks, and the wife found that she was able to remove her nose piece completely and just clear her ears with swallowing, which she'd never been able to do with her regular mask.
The safety factor is one of the best reasons to own this type of mask, in my opinion. If you're having trouble, you can tell your buddy exactly what's wrong. You can also locate someone if you're out of sight of them because the transmissions become decidedly clearer and stronger if you're heading in the right direction. Conversely, if you're going the wrong way, and not getting closer to your panicked buddy, the transmissions get weaker. Right after we got the masks, we were at about 60 ft., and I had foolishly used the wrong kind of sunscreen on my face. I was so warm, I started to sweat under my mask, and the sunscreen ran into both my eyes. I was wearing hard contacts at the time, and it stung so bad, I literally couldn't open my eyes. All I had to do was call my husband, tell him my problem, he came over, took my arm, and escorted me slowly to the surface. I was able to take the mask off, carefully rinse my face, and resume my dive. As we were ascending, he was able to call our dive buddies and let them know what was going on. They hung out in the area we'd last seen them, we went back down, and we all continued our dive happily. There have been times one of us has noticed a tank slipping out of a BC, or some other little equipment mishap about to happen, and you just say " hang on, let me get over to you and fix your strap". God forbid there's ever a real emergency, but I feel a lot safer knowing we can communicate what's wrong.
One of the other great things about them is --They Never Fog!!!! No more spitting, or soap, or goop-- I mean, They Never Fog. Really! You never get dry mouth either, or lock jaw from regulator fatigue. You never have to wonder if you just swallowed a bit of water that came out of an over water latrine on that tiny, picturesque island you're diving off of. You can point out the manta ray to your buddy who's enchanted by a nudibranch the size of a pin head. Or if the dive is getting really boring, you can discuss your dinner plans. The possibilities are endless...
One thing that does get annoying-- as the years go on, we find that the skirt around your face seems to take on a life of it's own, and mysteriously start to leak air out. We've tried several remedies for this ranging from waterproof surgical tape, to surgical tubing (no, we're not doctors) to finally weatherproofing tape. What you have to do is work whatever material you're using into the crevasse that isn't conforming to your face, to fill it out to stop the leak. It's a little hard to explain, but if you're going to a remote dive location, you definitely want to have something with you to stuff into the skirt, or it will annoy you no end. Oh, another thing--- everybody will want to tell you you'll use your air up faster because of the talking--absolutely not true. And God knows I can talk.... Maybe the first few dives, but again, you'll learn to talk in a way where your air consumption will be the same as it always was.
As to the Neptune mask, we did start out with those, and didn't like the way they fit. We got rid of them for the AGA, but again, we're talking over 10 years ago, so if you like the Neptune, I'm sure they've changed things since we wore them, and I'd say unreservedly, go for it! You'll love having a full face mask!