OMG!!! 700 polos with vinyl??? you're a hard worker. If that's the kind of work you do usually, I'd recommend you to setup an small screenprinting machine with 6 colors and 6 tables. If space is a problem, maybe a 4/4 machine. Always with microregistration, to align precisely the colors over every other. Screenprinting is not easy, as isn't embroidery. You'll have to learn how to prepare artwork, color separations, printing positives, exposing screens....but when you have it mastered (there are lots of tutorials, videos, etc. on internet) screen printing is very very cool. It's way faster and cheaper than embroidery, vinyl, and of course DTG and it's very forgiving with certain things. Example, if you print with plastisol ink, you can stop printing at the end of the day, leave the machine and the inks as they are, and continue next day without problems.
Regarding DTG, if you print a decent quantity of one offs, every t-shirt different, you could justify the cost of a machine and the ink. Advantages are: Clean environment, no screens, no positives, high quality printing. Disadvantages are: High price of machine and inks, very strict maintenance, need to pretreat every dark garment you print, actual inks not suitable for athletic printing neither workwear.
Anyway, every process has its own headaches, as embroidery with thread tension, needles breaking, etc.
