I haven't heard the two compared but I do have a Ultra paired up with a REED 12" arm, I went with this combo after going over to a freinds place and hearing the same combo numerous times and really enjoying what I heard every time.
Over all sound characteristics will differ like with any cart as there are so many variables that come into play, set-up, settings, associated gear and on.
My friend also has a Lyra Olympus paired up with a Shroeder Ref arm, another wonderful arm/cart combo. Listening to the two I found more similarities than differences but really still haven't been able to put my finger on it but found myself enjoying the REED/Ultra combo more so I went in that direction for one of my arms.
There are lots of carts out there to choose from, for myself I really need to hear before dropping any coin on such so I can fully appreciate where you are coming from.
Getting info. as you are is still only a stepping stone and no garantee's what so ever and just opinions, I have found over the years if possible best to try in your own set-up or at least hear in a set-up.
Good luck and have fun!