I know this is an old thread, and my apologies for resurrecting it but came across it and thought I'd give my 2 cents. I used the UR44c as my mobile rig, and replaced it with the RT4. Why? Because of more than just Rupert's name.
I always liked the no frills, clean preamps that the UR series used(D-Pre). Nothing special or exciting about them, just good preamps that shows exactly what is on the other side of the mic. Then came the RT4, that has those same pres, and with the Rupert Neve transformers engaged they added something really awesome to the signal. Some top end harmonic content, and when driven sounds like very subtle saturation to make it cut through anything. The value of these pres really come to light during the mixing process. The way I see it is that instead of having four unexciting but clean pres, I now still have them plus 4 exciting ones. Worth the extra money right there.
I record in my home studio with it now more than my primary interface, and hardly ever use my external preamps unless needed for a specific sound. I was hesitant to purchase it at first thinking the extra cost goes for the name(like most others believe), but the subtle mojo it adds has great results.
I try my best not to get caught up in bro science and taking other's opinions as gospel(and as such make excuses not to get product X or Y), but rather test and see for myself. It served me well this time around and completely changed my mind about the RT4.
Just my experience with it for anyone who's interested..