Range is not an issue. I use the ship (T9 or T10) in an isolated pocket of 4 systems, 120Ly from anything else. In that pocket cluster the max range between any two systems in no more than about 12Ly.
Also I'm not massively hung up on the exact cargo capacity. If I was, I would have been using my cutter. But that is gathering dust in HIP 20277. Anything north of 400 Tonnes is ok. It'd simply down to deciding if I can make a better tank on the T9 with the new slot, and have a ship I love to fly and love the look of, vs, the T10, which will hands down do the job with no worries at all, but has a £%*$%" spoiler and looks rubbish.
On the plus side, If I do ditch the T10, and go back to the T9, I still have all the engineered components for it, and all the ones I just finished doing no the T10, so I can pick and chose the best ones.
Hmmm I am really leaning towards the T9 again. When does this change come in?
If you can get more cargo from the type 9, you'll make more money.
But if money isn't an issue, fly what's more fun.