Digital BW, The Print

I wish to scan some of my old work and print approximately 12" X 15"
prints on an Epson Photo 2200.  I can get a drum scan locally at 100
dpi, 200 dpi and 300 dpi.  Would someone please explain how to
determine what I need?  Does it depend on the printer or are the ones
available all about the same?   Soon, I may purchase one of the new
Epson printers, for example the Epson Photo 2400.  Since the scans are
expensive, I would like to scan them today with the newer printers in
mind.  Thanks in advance.

Andrew.