Glidingdoc wrote:What is the difference between the 550 and the 750?
The 450 is just a Com, the 550 has VOR and the 750 also has glideslope and GPS.
Regarding the comment above about buying the 550 and then realising they did the 450, the 450 was released later, so may not have been available when you bought the 550.
I bought the AA battery version of the 550 which was actually cheaper than the 450 when it came out, as the 450 was only available with the rechargeable battery. Not sure about now. The designation "L" at the end denotes having the rechargeable battery and charger.
The 250 is smaller, lighter and cheaper with just a Com facility, but it seems to work ok. Don't suppose you get the big list of previously selected frequencies on the screen at once like you get on the larger (bulkier) ones though.
Yaesu/Vertex Standard isn't completely a new name in aviation. I've also got a VXA-700 from some years back and even that wasn't their first generation of aviation products.