A DSLR has numerous advantages, with main one being no shutter lag and exchangeable lenses. the problem there is that all these lenses cost money, and the better ones cost much more than the camera. For macro photography, which seems to be where your interest lies, expect a macro lens in the 60 to 100mm range to retail new for between $500 and $700.
As far as better pictures go, the DSLR tend to have a larger censor, which does help with picture quality. New models with more megapixels come out often, so perhaps an older model might offer better value, either new or slightly used. I have a Canon XSi, and like it a lot. I chose Canon because I know several people who shoot Canon, which gives me the opportunity to audition/borrow various lenses. Even the most basic DSLR in a company's line will offer lots of features, and any ( well, most) lenses you acquire will work on a new model if you decide to upgrade.
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