This is just my opinion and experience based on the one Epson I have ever owned:
We have an Epson SureColor S70670 running GSX inks and it was by far the worst printer I have ever owned. One of the first wrap jobs we did was a heavy on the orange. It faded so fast, within 6 months we had to redo it because client was very upset. Only then did we find out the orange was only warranted against was only 6 months. Odd since it was marketed as wrap printer and I don't know anyone who only wants a wrap to last for only 6 months. We now avoid orange ink like the plague and setup oranges to M/Y mixes.I don't know if they have solved that with newer inks. Good luck trying to get 2 panels out of it that are the same length. We can get variances of 1/2-3/4" over 8'. The dealer originally tried to work with us to solve the issue since we were told it should be less than 1/8 over 8'. The dealer finally threw up their hands and passed us off to Epson who told us that 1/2" was with in their tolerances but they don't guarantee any repeat-ability for length. We also got the silver and white ink option. The silver basically just rubs off with your fingers on any media and clogged constantly and we have never used it. The white was ok but clogs often and we use more in maintenance than we actually use printing. The white is the only reason we still keep it. Need repairs? Almost nothing on it is self serviceable so be prepared to spend a lot replacing heads or other repairs. You can't even bypass maintenance issues in a bind. If the controller says it needs to be serviced it bricks the unit. In addition, Epson subs out repair so the quality of the repair is completely dependent on the skill of the repair tech and how easily then can figure things out. At least with our Mimaki, you can limp along on one head or replace heads, damper etc when you are in a bind.
HP's biggest issue is the time it takes to start a print and the amount of material you have to waste for a leader but it is a work horse for long runs. Starting a print takes for ever so if you are bouncing around with different material for each job, you have a lot of down time. We never have nozzles drop out or at least we don't see it since it remaps bad nozzles and being able to swap a head in a few minutes is a tremendous advantage. The print quality on a HP is much more clear and crisp than the epson making it much better for small sticker jobs. When it needs schedule maintenance it warns you well in weeks advance so you can plan down time. Most HP repairs are kits which makes the quality of repairs completely predictable since the repairs are essentially plug and play. Unlike the solvents printers we have, HP give you a fixed price for the repair and it is always fixed right the first time. With Epson, they'll fix one problem and leave and then something else isn't running quite right like maybe the head are slightly out of register or an ink line isn't plugged in properly etc.
I think what we have learned is there is no one printer perfect for every job and it is nice to have a mix. Keep in mind the folks making or selling this equipment don't have to make their living running it so they tend to down play what it actually takes to use these in an actual shop environment.
...my 2 cents..