Dex does a lot more things for us than Presence, but Presence is a low hanging fruit that has immediate effect. Note however that those effects aren't that big. Our only art that really uses Pen currently is FSS, and here is what we have:
With Presence D, we'd have +15, so B38. It is significant but not groundbreaking, and it is even moreso once taking into account that Call to Ending ignore armour anyway (so pen is useless for it), so our trump card doesn't care for it.
However, Dex influences P.Avoid, Initiative, Stealth and Speed (Eww).
With Dex A, we'd have +15 to speed, +15 to Initiative, +20 to p.avoid and +15/20 to Stealth. In practical term, as we are getting Athletics C anyway and we are getting SCS8 and PLR5 by the time we'd have Dex A (in two turns) this means having something like A Speed. It means having B15? Initiative (not sure we are getting any more from other sources). Most importantly, it means A13 avoid rather than B33 natively. Stealth is a bit harder to analyse, as the current plan doesn't get us a stealth art and as such it decides we don't really care about it. However, even then it likely means having B37 rather than B17.
Basically, Presence is a long term investment even if it gives an immediate rank up, while Dex gives a longer rank up but is an immediate pay off.