DeepSix, I use bluecharts and find the detail to be exceptional. I would of thought all charts would be basically the same as they are all scans from the actual paper charts. The additional bits and pieces you get are from the sounder themselves, such as tide times and celestial information for your local area and I know Garmin units have that info on their Bluecharts.
The best option may be to go to a store that displays all the brands and look at the detail and options that are available that suit your requirements.
Cheers, Mick