Modern Vespa

As Jim already said, the top speed of the 250s we own is just about 80, but we don’t ride them at that speed. While we haven’t ridden 300s, I’m pretty sure they are similar when it comes to top speed. Her’s is 15 years old with about 15K miles and mine is 12 years old with about 22K miles on it.
We do appreciate the ability to jump on the Interstate (our’s is called The Northway from Albany to Montreal) for an exit or two where the ability to do 65-70 in the right lane gives great flexibility. But that is not the reason to choose a big frame. The reason to own one is its ability to have all the power you need to be safe and comfortable on any two lane highway, even mountainous roads, even when you are carrying a lot of extra weight.
The reason my wife wanted a small frame was to have a scooter that is easier to put on the stand, to maneuver while parking it, and she thinks it is more nimble. And she does love it.
She rides it into town to the gym. But, we live six miles from town center, and the road home is uphill with a 55mph speed limit. She is running some of the way home full throttle. Not a problem as most drivers don’t speed on this particular road, but I prefer not riding a vehicle at its performance limits.
Where you are in Naples, most of the roads are boulevards and a 150 is adequate; 35-55 is all you need. But would you want to take a 150 across 41 to Miami? With a 250, it is exactly the right bike for that road.

On the other hand (just to be contrary! ) it can be more fun pushing a smaller powered bike to its limits rather than constraining a bigger bike to your own limits as a rider.

But personally I'd rather it was a GT200 than a 125 or 150.

Lots of good points but I'll throw mine in. I think the bottom line is if you are riding intercity vs. more open roads and how big you are. I started with a 2007 LX 150 and I love it. I ride it all around town and commute to work on it every day. It is very light so it is super easy to park in tight spots and easy to maneuver. A year later I found a great deal on a lightly used 300GTS. It is totally different and I loved it also. Much more powerful and larger than I expected. Works super well on higher speed roads and more comfortable. But, I found it more difficult to park and maneuver. I work at the airport so I park in a hangar around lots of planes and tight quarters. I am a small guy (125 pounds) so I didn't like the extra weight of the 300 and it felt less flickable around town which is where I ride the most. I also didn't like the headshake. Mine had the heavy bar ends but when I would let off the throttle it would headshake unless I was very slow to decel. I have owned many motorcycles so I have experience with larger more powerful machines but I ended up selling the 300 a couple years ago. I just bought a 2020 Primavera 150 and wow is it nice compared to my 2007. It is much smoother and more quiet. Performance is pretty similar but it feels much more stiff and rigid, maybe because it isn't 14 years old. I love the fuel injection, ABS, LED lights. I love all Vespas but for me I wanted to find the best fit for what I do and for me that is the 150. In my business we have a saying. Buy the aircraft that does 80% of your missions best. You could probably apply this to scooters as well.

I'd say that is good advice. Just be sure you have defined the "missions" to be undertaken and the capabilities needed to succeed. Mission creep is not unheard of .

If you can’t make up your mind about which one to buy, you can always do what I did and buy both of them . However, in my case, my lower displacement scoot is a Genuine Buddy 125 that I use for short trips and errands. It’s also nice to have a back up when one of my bigger Vespas goes down for repairs or maintenance.

I bought the 300 first and i was up at my Vespa dealer and saw the 150 S model with the digital dash and i couldn't resist .Before my 2017 White 300 I had a 2016 Black Super but i blew the engine so i ordered/bought the white 300 as i always loved white . So i now have the best of both worlds