There are a variety of types of caps and they have various benefits and disadvantages. I use pens in two ways: writing drafts like this one and taking notes when reading and researching. Taking the latter first – and why not? The best cap for note-taking is no cap at all! I had a Pilot Capless for a few years and it was convenient and a good writer. Too convenient, perhaps, because other suitable pens never got an outing to take notes. In the end I sold it. It was a good pen and I enjoyed it but it was time to try the other pens.
I had a Lamy Dialog briefly. It lacked the convenience of the Capless. Twisting to expose the nib is not one handed, or at least not conveniently so. The pen was heavy and did not sit well in my hand. The new Platinum Curidas has yet to come my way. I have no doubt that it will.
Pens that have caps that must be unscrewed are a nuisance for note-taking. The hard rubber slip caps of the earlier part of the twentieth century were beautifully machined and those I’ve had fitted firmly a century later. It is my one use for eyedropper fillers.
Modern pens with press-on caps depend either upon a plastic clutch, or, more simply, several small protuberances that close the pen against the section or by locating behind a ring. I do use such pens for note-taking but I do not expect that they will still be usable in a century from now. Clutches and bumps wear. The former is capable of being repaired, maybe a few times before it gives up altogether. I can imagine a rough hack that would replace bumps but neither closure method is especially durable.
That takes care of the note-taking. For more extended spells of writing any pen will do. I don’t post my pens. Once the cap is unscrewed or pulled off it is set aside until I’m finished so threaded caps, even those that take several turns to uncap, are perfectly convenient. Other concerns become more important – the comfort of the pen in the hand, the quality of the nib, even how many pages can be covered before a refill is required.
Like most people, I like pens that don’t dry out quickly and the cap plays a large part in that. The Platinum 3776 is most famously secure in that regard but most pens, old or new, can be set aside for a week or two and still write instantly. I have two Swans that I particularly favour, a rather battered SF230/60 and a 1060. Either could be set aside for a month or two without drying out. Mabie Todd made good, well-threaded caps.