There is only one advantage
There is only one advantage of having the InfiniTV4 hosted by the always on server… when the HTPC wakes up, the tuners are instantly available from the server… there is no minute-or-so authorization time after wake-up like there is when the InfiniTV is in the HTPC.
That said, I have a WHS 2011 machine and I still run my main HTPC with the InfiniTV local, as I just don’t trust the network that much to rely on it to record my favorite shows. That and I don’t watch live TV that much (almost never) to care about waiting the minute or-so it takes for live TV to be available.
If you watch live TV often, and like the cable-box feel of having live TV instantly available after wake-up from sleep, then host your InfiniTV in an always-on server, or never allow your HTPC to sleep.