Personally all being even, I think you get a better imaged mug with a wrap, with an image closer to the handle and closer to the bottom of the mug. The oven heats the entire mug, and not just the outside, near the handle. The handle and the bottom "sump" the heat and does not get as hot as the other areas of the mug, so your image may lighten a bit in those areas. If you are doing mostly single mugs, and want to do them quickly, than a press will heat up quicker, and may be better for your business model. If time is not that much of an issue, then you can use a small Hamilton Beach Convection oven and have a mug in about 15 minutes. The bonus is that you can do up to 5 mugs at a time in that oven, so your throughput could be higher than a single mug press. Also, by doing 5 mugs at a time, you don't have to change them out as often, so it can be easier to multi-task and do other things while the mugs are "cooking". If your volumn really goes up, you can add another small oven and double your through-put or add a larger oven and do large quantities at a time.
Once you get your time and temp down with your wrap and oven setup, in my opinion and experience there is a lower mug scrap rate, than with presses. That is presses in general. Of course there are lots of different presses and they all have defferent scrap rates based on their designs.
I have talked with lots of people, and some like presses and some like wraps. You could always get a single wrap and try it and see of you like that process. Hope this helps.