If you plan on getting the SS1 remember that you will need to breath from it while venting air from your BC as you ascend. Make sure that this is easy to do and doesn't add any additional task loading.
As has already been stated if you get the SS1 you need to make sure that your primary second stage is on a hose long enough for you to comfortably donate to other divers in case of an OOA situation. If you don't do this then you might as well just forgo the SS1 and dive with only one second stage (I don't recommend this).
The problem then becomes dealing with the longer hose. If you route it the traditional way you have a larger hose loop out to your side which can catch on things, etc... I personally feel that even a traditional length primary hose creates too large of a loop as I have had it catch on things before. One solution to this is to route the hose under your arm instead of to the side. To do this you put the hose straight down off your first stage and use a swivel on the 2nd stage.
While this last solution works fine, I prefer a long hose. I find that it actually routes the best and despite being longer is actually more out of the way. It also gets rid of the jaw fatigue problem without needing a swivel and as such lowers cost and removes a possible failure point from the system. It also makes that big hose loop to the side much smaller. If properly routed a 7' hose stays completely out of the way, and gives you plenty of hose to work with when you need to share air. I help out with scuba classes so I have had plenty of chances to practice air shares, and while a traditional length octo hose works it is far from the easiest and most comfortable solution.
If you do end up getting a long hose remember that you should not leave a snorkel on your mask when using it and that you need to practice air shares with it in order to get used to it. That of course goes for any of the other options you have to choose from as well.
As far as the Z2 vs. B2 goes I personally would go with the Z2. I personally find the 1st stage swivel to be completely unnecessary. For me it adds weight, size, complexity and an additional failure point while not having any advantages. With a traditional regulator setup the swivel does allow for slightly better routing, but if using an SS1 or a long hose it no longer becomes beneficial. The environmental seal is another feature that you do not need unless you plan on diving in very cold water. It adds about $20 every time your regulator is serviced so if you don't need it then you are most likely better off without it. It can also be added at any time so you can always decide to add it later.
~Jess
