The best digital printer will depend on your budget and production capability requirements. There is plenty of choices when looking to purchase a DTG printer, with the option of used or new equipment.
The fastest DTG printer is the OvalJet which produces up to 240 prints per hour, with one operator.  It produces the best quality prints, at the lowest print cost. more information can be found here: https://www.adelco.co.uk/digital-printers/ovaljet