I believe there are other things that determine the quality as well: Resolution Enhancement technology (found in laser printers also), quality of paper used, quality of ink, size and placement of the ink dots, to name just a few.
A 720dpi printer isn't necessarily better than a 600dpi printer. Another significant factor in print quality is the number of ink cartridges in a printer. Some use a single cartridge design, meaning if you print in black only, you put in a black cartridge; and if you want color, you put in a 3-color cartridge. This system then mixes the 3 colors anywhere black is needed on the page, which produces a lighter washed-out looking black. It also uses a lot more ink, slows the printing process and soaks the paper.
I recommend a dual-cartridge printer, which prints faster, provides superior output, and saves money on ink. I also recommend prioritizing your interests of importance based on your needs is the first thing to decide before settling on dpi's. Followed by the affordability and desirable quality.
Always get a sample printout. Deciding on which is the best is best answered by you and your needs. You are the one that has to be satisfied with what you see and what you interpretate as looking good. We all have different views and perspectives. Good Luck!
JustOneBrat