Many people have reported less Power supply failures with 220 / 240.
Personally, I think it is because many of those people are also using server power supplies @ 240 and have already burned up the POS Bitmain PSU, but I ran one S4 on 110 and 240 and had an equal number of Bitmain stock power supply failures.
1. I would not overclock using stock PSU on either input voltage
2. I would replace the stock PSU as quickly as possible with a server model, IE DPS2000BB works beautifully and can be made to fit inside the unit, albeit a bit messy and I would never resell it that way.
If you are ever looking at S4+ units, they are 220 / 240 ONLY and have crap QC on the power supply.
My "mining room" happened to be about 2 feet and one uninsulated wall away from my breaker box, so I ran a 60amp 220v feed (with an electrician friend's help... it's a fairly easy job but one mis-step can lead to at the very least severe injury and at worst death) into my hashing room. Dual phase is the way to go if it can be done economically.
It also has the added benefit of opening up the 1300watt+ range of PSUs to you (and they tend to be cheaper due to lack of demand). I picked up a lightly used 2000watt IBM Bladecenter PSU for under $25 shipped to my door, like most PSUs in this range it's just a rebranded Delta 2000BB, I did need to install a fan because it did not have one and I really didn't want to fry it. If you're comfortable with that sort of thing it can be a very economical way to power your equipment, I have a third S5 on the way and I'll be able to power all of them with just a single power supply. The benefits, while slim, when combined with the cost saving make it a no-brainer. I'm nowhere near stressing this PSU out, even with 3 S5s running on it, I'm also generating less heat, wasting less power (some will debate me on that, I'll know for sure in a week when my HP 1300watt PSUs arrive), and it was something I hadn't seen done yet and wanted to take a crack at. I've bought a second one which I'll duplicate the mods from my first PSU and install it ready to go for an easy swap in case of failure. It's not a good idea to have a single point of failure if at all avoidable.
IMO if you can swing 220V do it, and if you're doing a new run I'd also go overboard with amperage. I'll post more detailed pictures of my setup and the modifications to the PSU (Full disclosure pin-outs came from RC-Universe, they're all over the server PSUs for whatever reason) later this week once I've got it not looking like a total mess/embarrassment if anyone is interested. I'm quite proud of it.
