Ah! Someone has opened a REAL can of worms here!
I don't know when Levy tried Sprint last, but a LOT has changed recently.
About 5 years ago I tried them and wouldn't touch them again with a 10foot pole.
But now, their customer support is actually *good* (you get a live rep within 2 rings, who speaks english and is helpful), their data network is TOP-NOTCH (I'm getting EVDO Rev A. out here in the boonies, with 2+ mbps... Verizon still averages 0.8mps out here with Rev 0), and the final blow, I have reception EVERYWHERE Verizon does, literally.
Levy, in case you didn't know... Sprint now has a roaming agreement with Verizon. So, whenever you don't have Sprint, you switch over and use Verizon's network for free. So, better reception is NOT a valid reason to stay with Verizon anymore (it may have been a while ago).
Now, personally, there's a million reasons to leave Verizon (I literally HATE them after seeing how they treated me and other customers- they are the "bully" of the cell phone world and don't really care enough to keep your business- they get the latest technology after the other carriers have had them, cripple features on their handsets, and overcharge for almost every feature... but people are on them because they're established and have been around, and have the "better signal" myth), but that's not really what the point of this thread is.
I could go on all day about smartphones vs. Blackberrys (and I appreciate that you recognize the blackberry isn't REALLY a smartphone), but I'll keep it simple here.
Bottom line: Its a personal preference, and neither is better for everyone.
Blackberry does what it does very well. Its easy, its straight-forward, it works.
Smartphones and PDA's, however, let you do literally ANYTHING possible since they have operating systems that allow you to install new software. Basically, any new features you want you can add by writing or installing a program, whereas the blackberry will always be limited to what it does out of the box.
Case in point: When wireless stereo was becoming a standard, new phones were coming out that supported it so you could play your music on your home or car stereo in high quality without wires using a variation of bluetooth audio technology. My 3 year old smartphone had bluetooth, but not the support for the stereo profile. I installed a program and BOOM, I had bluetooth stereo support (A2DP). Then I wanted to be able to browse shoutcast internet radio on my phone, so I installed a media player that allows that format. Then I wanted an easier way to look for stations (their site is hard to navigate on a mobile browser), so some friends and I starting writing our own shoutcast program that parses the information and makes it easy to search and find and play internet radio stations.
There's an endless amount of features you can add to a smartphone/PDA to make it work better for you, its the customization that makes it worthwhile (I've even designed a system for someone to open their garage door with the smartphone). I beleive that what someone needs varies from person to person, so that level of customization is a MUST for me. However, I do recognize that many people do not want or care to spend the time to tweak their phone to be perfect for THEM. In that case, the blackberry is a much simpler straight forward platform. It has less features, but many less-technical people will see that as a g-dsend.
I'm not sure if I'd go this far, but I've heard the blackberry referred to as "smartphones for dummies".
By the way, I wouldn't dare get a data plan on Verizon unless you're willing to spend $80+ on your bill for voice and unlimited data. Sprint has a special SERO plan (Dan's a big advocate) where for $30 you get unlimited data and 500min of voice. Combine that with a decent smartphone, and you can't beat that deal anywhere.
Whew, what a long post for too early in the morning for me. Hope it helped.