OK its really pretty simple as I see it and there is no real winner here. Lets start things off by build quality. Both phones look nice from a distance but the Thunderbolt looks more complex and expensive and the Charge looks more mass produced by a big electronics giant Hmmmm. I thought I would really like the real keys at the bottom vs the touch keys turns out I don't although the keys work nicely on the Charge it seems like having to push them in an unnecessary extra step in todays world. Power and volume buttons are much better on the Charge without a doubt. I do like the kickstand on the Thunderbolt it gives the handset a little extra feature that no one else has if you know what I mean.
Getting down to the nuts and bolts now on how they function is where the real difference is in my opinion. Now I have only used the Charge for one day but I can tell you this hands down the Charge just works better in almost every aspect. Not by a lot but its noticeable once you have used them both. First of all the Charge pushes 3rd party emails almost as fast as a Blackberry I'm still amazed my AOL mail arrives within 3 minutes every single time and Gmail is of course even faster. The video camera works much better on the Charge the sound is so loud and robust and clear that even after the Thunderbolts update it still makes the Thunderbolts level of volume poor. Battery life is slightly better on the Charge as well. The Charge's screen is amazing but the Thunderbolts isn't all that bad either.
Over all reception is about the same on both phones the signal bars are just about the same. Call quality on both phones just about the same. Touchwiz is laggy and just not as smooth as the HTCs sense. The Charge connects the hot spot faster and has a much better sub menu system for the hotspot it even tells you the devices names that are connected to it. Not to babble on and on my feelings are like this if you want a beautiful runway model in pretty pumps but sometimes forgets what planet she's on buy the Thunderbolt. If you want a pretty housewife that washes the floors and cooks you dinner and picks up the dog poo buy the Charge. So what am I really saying? They both work well but internally the Charge seems to work better, it's operating system seems to be more stable.
I just love it when people who switch phones feel the need to go back to the forum for the old phone and give their "honest review" of the two phones in an attempt to justify the switch, especially when the reviews are vague and/or don't support their conclusions.
So your main reason for switching was third party email support which you say is faster on the Charge. Fair enough I guess but there are third party email apps of you don't like HTC's. You mention functionality in every respect but give very few examples and I have to point out that Thunderbolt will probably get enhancements to provide a similar experience with the Hotspot app in a future update.
You mention that you think the Charge is faster (less laggy) after owning the phone for one day. While don't own a Charge, I have spent a good amount of time with store demos (after rebooting them of course) and own a Fascinate (which also has TouchWiz on it) and I have to question this as well. Sense is without a doubt the smoothest user interface I have ever seen or used on Android in my experience with the TBolt, Dinc, DInc2, Evo, and Eris. The only Android phone I have used that was actually faster response time than my Thunderbolt is the original Droid after the Froyo update (no Motoblur or third party launcher). The Fascinate felt super fast when it was new, but once I added a few apps to it (like 50 I think) it started to majorly lagg and while the Charge is a newer generation I have a hard time believing it will be any different.
You are in the significant minority if you feel the build quality on the Charge is anywhere near as good as the Thunderbolt. Even the TBolt's critics give it that ("it is a very well constructed phone"). The Charge, while not quite as plasticity as the Fascinate, is not even a close comparison here.
And last but not least, you may want to avoid these forums thus summer when we are all feasting on Geiger-bread and you have to drown your sorrows in Froyo because your Gingerbread wont arrive until at least Christmas if not later.
We all appreciate your taking the time to compare the two but you might want to give it more than a day and perhaps a little more in depth thought rather than just initial reactions next time.