If you need a timepiece for mdr nav it needs to be easy to see and big enough to read.
1)Even with a sweep second hand a wristwatch satisfies neither of these as it is seldom possible to read the minutes.
2) It is on your wrist and therefore out of easy vision/scan.
3)The stopwatch buttons are almost invariably too small and fiddly to be satisfactory in practice.
4) operating it takes both hands out of action simultaneously which isn't the best of ideas.
If your aircraft doesn't have a suitable stop-clock/timer fitted (!) you may need a traditional 2 inch size stopwatch with a big, positive click action - preferably analogue for ease of reading mounted on your clipboard or on a mount on the yoke or panel. They cost probably under £40 new on ebay.
AGAT Vintage military Russian USSR pocket mechanical stop watch chronometer EXC | eBay
One of these, or similar is simply unbeatable for ease of use.
Accuracy simply is not an issue for practical purposes, even if it gained/lost 30 seconds an hour (it will be far, far better than that of course) it's more than accurate enough for nav.
Wristwatches are nigh on useless for nav, "pilot's" watches with those three tiny dials that are completely impossible to read accurately, if at all, are for posers and Walts. They are a waste of money.
I very much doubt any serious pilot uses one for real. Certainly in my 15,000hrs of very varied flying I've
never once seen anyone use one. (No doubt I'll be bombarded with Typhoon pilots saying otherwise but I remain sceptical)
Those that sport the brick-sized bling variety tend to be PPLs and low hours rich-daddy pay-to-fly FOs. Or ex-fighter pilots - see line below. After all, everyone knows £50,000,000 fighters don't come with clocks...
Still, if you imagine it makes your willy look bigger...
Mickey Mouse for me! (seen several of those over the years - often on very experienced wrists)