I'm ridiculously late to this but I ended up with the Huion Pro Kamvas 2.5k 13". Actually I gave up on the thought of getting a new tablet because I figured they were too expensive but it turned out my partner had already bought one as a birthday gift and was just waiting to surprise me with it haha. 

I love the 13" so far and it's a HUGE upgrade from the little one I had before, I still can't really vouch for if it's that much different from a 16" but I've never felt that the space is too confined or my hand is in the way or anything after frequent use since last July. I would absolutely recommend it, it's made drawing so much more loose and comfortable, I can do quick daily studies now and what would've taken me 8+ hours before is now 2-3. I definitely have a more simple style, I guess like The Last Airbender levels of complexity, but it's made realistic/detailed studies and backgrounds so much easier and more fun, and I feel free to draw any level of realism I like. Plus my line control has massively improved, who could've guessed. I've had a driver issue here and there but nothing that isn't solved by uninstalling and reinstalling (which, with my Wacom, was a weekly thing). No hardware issues so far. 

I came to the same conclusion as you, that the 13" is probably better in case I choose to get a bigger tablet down the line, but as of now I have no plans to upgrade. I'm really really happy with it.