well I don't have the two yet.. but i can make some comments based on what I've seen.
Overall the dimensions are extremely similar. The barrel length and the slide length are about the same length. However, if you consider either as a ccw then you realize that this length really isn't what tends to make carrying difficult.
The "height" of the pistol or the grip length is what tends to print while carrying. And this is where the 245 is a bit shorter than the 220. Now since I don't have the 245 yet I can't actually comment on the difference, but all in due time.
As to feel the 245 feels like a slightly shorter 220, which is what I would hope for. Some people have complained about the 245 being so short that they can't get comfortable with it, but that tends to be subjective to to the user. You're best off trying to handle one and get some rounds through it.
I myself felt a little aweward the first time shooting a 245 but it was so accurate and similar to my 220 that I began my search for one almost immediately after putting some rounds through it.
As for more rounds. The 245 does indeed carry only 6+1 versus the 220 8+1, but 220 mags do fit the 245. So with a reload you are in the same ballpark as a fully loaded 220. Initially you are trading off 2 rounds, but you aren't further handicapped after the initial reload.
I'm sure someone will chime in with both that can further the discussion, for now at least I'm still waiting on my 245....
UltimaSE