I have a Mutha Hubba and a Copper Spur UL4. To be honest I'm not sure you are gonna gain much by changing. If the Hubba is in good shape I would find another backcountry item to spend the $$$$ on. They are both great companies and make great products. My Hubba has seen tons of use and is the most versatile tent I have. I love it.
I have the Hubba Hubba and a Fly Creek UL1. The thing I dislike about the Fly Creek is the front entry. You have to crawl in and out. The vestibule is not big enough for much of anything but your boots. I realize that it is hard to compare a 1man to a 2 man tent but as soon as I find another 1 or 2 man tent that I can save weight on the Fly Creek is going to the classifieds.
I really like the Hubba Hubba. The only reason I have not used it last year or this is I am really trying to cut as much weight as I can.
I have the UL2, and I love it so far. Looks like the Fly Creek is lighter and more packable than the Hubba, if those are big issues, it might be worth it for you. Reviews against other light 2 man tents have put the Fly Creek UL2 at the top of the list.