There are a few different observations from your post.

Firsty, despite the introduction of the X45 I still don’t really see a big increase in the number of smaller jets. I am a small jet fan and this is quite annoying, but there are many more options available in larger sizes.

Small jets vary significantly. For example, the Habu 32 that many converted to Jetcat P20 flew really well, but it had the traits of a small jet (relatively high wing loading and somewhat twitchy/snappy if not set up right) whereas I also fly a Sebart Mini Avanti which is extremely easy to fly in comparison.

I don’t think anyone would really argue that the larger jets are generally more stable, but that has to be balanced with ease of operation. I have probably ten times as many flights on P20 models than my bigger models as I can chuck them in the car fully built and get 2 or 3 flights in whilst everyone else is assembling their models. The size also has the added advantage that if it starts to rain you can put it straight back in the car.

Also, some (not all) of the smaller models are cheaper. I can completely replace my mini Avanti for the same price as a landing gear set for a bigger model.

If you have a big flying area, lots of time and what the best flying model then I would go bigger. If you want ease of transport and quick/easy assembly then smaller models are worth consideration.

Or the best option, is to have at least one of each!!