From a comfort perspective: deployant, or tang buckle?

In my view, the overall quality, fit and finish of the strap material itself is far more important than the type of buckle. The best looking, highest quality buckle won’t make a mediocre strap any more comfortable to wear.

There are all kinds of deployant buckles, I've not had one that was impossible for me to wear, and I've only had one that failed when the pin broke off when I was adjusting it. A really nice buckle is the Artem RM style that is US$73. For those that aren't familiar with the Richard Mille design (also used by some Blancpain and Harry Winston models) it uses a leaf spring to keep the buckle closed, no push buttons or friction closures to mess with. It's very secure and taking it off/putting it on gives a very good feedback and quality feel. It is attached with a screwed bar on the buckle end which can be fiddly to attach because you are working blind inside the strap, but once it is on it is ultimately secure. Worth a look, I've got three and have been very happy with them.
RM Style Deployant Clasp - Stainless Steel (artemstraps.com)