I think the 28 has the best compromise between size and floorplan. It's the smallest model with a full sized bed, dinette, and sofa. Our 25 is also good, but the bed is smallish and difficult to make in the corner.
On the other hand many state park, national park, and national forest campgrounds have length limitations. The 28 will keep you out of some spots.
A new trailer will depreciate quickly. If you can find a slightly used one you may come out ahead if you decide to sell in a few years. But shop around carefully.
I bought our Safari new at a dealer in Dover, FL for 25% discount off list, which was cheaper than the 1-3 year old used ones I could find at the time. But see my 2003-2004 posts about the dealer experience...