That is a very long winded and opinionated answer I'll try and give you the short answer. Dtg is a very new process and still being upgraded all the time it uses water based ink so it has a much softer feel to it also takes up a lot less room in your house or shop it does have a steep learning curve to it but once you have down dtg you can do one off shirts a lot faster.
Screen printing has been around forever and is the workhorse of the printing industry. With all of the videos out there it is fairly simple to print a easy design but not very time friendly if you are only doing a few shirts. Even though you can use water base inks most do not so the print has a heavy hand to it.
If done properly both prints will last a long time maybe equally as long if just starting your company you may want to outsource your printing for a while and not do it yourself? Also what kind of clothing line are you coming out with the feel of the print and the garments to be printed on may make a difference also. hope this helps!!
Brother has a DTG (Direct to garment) printer, it prints the design directly onto the shirt much like a inkjet printer for paper. The ink used for the DTG fuses with the cotton fibers in the shirts, basically dying them, which leaves you with a soft vibrant colored design that wont fade or crack from washing it. The Ink fuses with heat from a heat press.
These printers are quite expensive tho.
Check out this site for more info http://www.brother-usa.com/GarmentPrinters/