The Samsung E700 is shown as Class 10, whereas the better spec E710 is shown
as Class 8.
It's not a 'Power' thing, its a 'Speed' thing ;). A class 10 device (under
the right circumstances and all else being equal) can send data via GPRS
quicker than a Class 8 device. When receiving data, there is no difference.
A GPRS Class 10 device can run exactly as a Class 8 device but it also
has the option of sacrificing some of the Downlink speed (i.e. fetching
information from the internet etc to your phone) in exchange for somewhat
better Uplink speed (ie sending information from your phone to the
internet/whatever)
As the Class 10 includes the GPRS capabilities of Class 8, Class 10 is
obviously the 'better' choice. When taking into account the other
differences between any two phones/models, you might well decide that the
difference is insignificant however. The Downlink speed will be the same on
both, so I guess it depends how much data you 'send' via GPRS.
Some details here, in case you did not already find them:
http://www.gsmworld.com/technology/gprs/class.shtml