I feel that all BlackBerries are smartphones, according to the definition of "smartphone" in the Wikipedia Encyclopedia, although it's quite subject to debate.
Here are my favourte links about BlackBerry versus other smartphones:
However, as a phone, you may prefer a model-7100 style phone, if you use the phone a lot more than data. However, if you use data a lot more than phone, you'll definitely prefer the 7250. Unfortunately, there's no 7100 style phone on Verizon, so you'll have to go with 7250 if you're with Verizon.
So, assuming you can live with 7250 as a cellphone. While the BlackBerry software market has exploded massively in recent months, there is still not nearly as much software for BlackBerry as for Palm, so you may have some difficulty finding such software. That can be a big problem for little niche-market applications such as a diabetes-related software program.
One route you can find out is whether there's any diabetes tracking software in "midlet" format for other cellphones (Nokia/Motorola/Sony/Siemens/Samsung) because you can install other java phone software on a BlackBerry too. So if there's a diabetes program for Nokia java phones, you can install that on your BlackBerry too.