Don't know whether this helps but I am a UK user and if you read this link, (it wont let me post the full URL for some reason) but if you add the usual start to a URL and then add the following
it gives a comparison, it is a uk page though but tells you the main differences (apart from the obvious)
I have an 8700g and have been very pleased with it. I do have other phones which are LG Chocolate and the Sony Ericcson W810i which have the camera, mp3 player, video etc (not sure whether it is the same in the US but everytime you go to a different company you usually get a free phone with the tariff).
Strangely enough I went into a 02 shop today just to have a look at the Pearl 8100 mobile since it is a multi media mobile which is what all my other phones have been.
To be honest multi media wise it is way behind what else is on offer, Sony are doing a 3 megapixel K800i all singing all dancing phone. The 8100 feels clumsy, the thing that really drew me to the Blackberry the qwerty keyboard is replaced by a fiddly keyboard. In my opinion my 8700g is the only phone which I constantly use all the features.
My other multi media mobiles are sitting in the cupboard - the novelty has worn off as I have a perfectly good IPOD for playing MP3's and a much superior 10 megapixel small camera for photos.
Therefore IMO the 8700g enables me to email quickly without messing around with a fiddly keyboard and hitting the camera by mistake.
If I had had the Pearl it would be sitting in the cupboard with my previous "must haves"
I hope this helps