Both the V4.5 and Uratama are great versions - similar characters, but otherwise remarkably different in gameplay. As EMF has said, the V4.5 has more games and is more interactive in terms of school, jobs, and the shop. On the flip side, the Uratama has cool items, secret characters, cooking, and a robot butler which is great for busy people. The Uratama also evolves at about half the rate of the V4.5, which for some people makes this version slow & boring, and for others allows a better caretaking experience.
I can't decide which I like more. They are both, in my opinion, some of the best Connection era releases. If you've got an Uratama already, perhaps go for the V4.5? The V4.5 really is a standout in the Connection line. Let us know what you think & decide! ^_^