I was going through the same thought process as you are right now a few months ago. I have a GHS machine as well and sold my Exmark to find something that could fit in all of my gates.
I ended up going with the MBK 23 EFI 48 inch mulch deck. Let me tell you I love this machine. It does an awesome job and I can't tell a difference between the cut this leaves compared to my GHS. The machine does great on hills, much faster than the GHS and quality of cut is just the same. In tall wet grass you might have to double cut, but the second cut goes very fast and I'd much rather cut it twice than bag it. No clippings to deal with at the end of the day. The deck will actually load up with wet grass before it leaves a bunch of clumps on the yard. Just be sure to keep the deck clean in wet conditions. I paid $8,000 before taxes for the machine and deck.
I'm now wondering what to do with the GHS. I need it for scalping some yards in the Spring and for some leaf collection in the Fall, but other than that it's a backup. I'm thinking about next season just getting another 48 inch mulch deck for my GHS unit. If you have any other questions I'll try and answer them, but this has been the best mower I've had so far.