I can’t offer any first hand opinions on the E75 (thought it wasn’t out till the 10th to be honest, so I haven’t used it).
As far as the E71 is concerned, @DrasticDreamer is fairly spot on, the E71 does have a decent talktime for a Symbian based Nokia phone, although you could probably take a few hours off the quoted times, as with any phone, but you would most certainly be able to use it fairly solidly for the day and not have any problems.
If the browser is really important, you’re not going to get anything out of the E75 that you wouldn’t with the E71. The E71 has a decent 2.36 inch screen (although smaller than its predecessors), and the browser is full screen, and also deals in landscape. It also has 128MD of RAM, and full support for Flash and Java. Can’t go too far wrong there. The E75 is only going to equal that, no way will it beat it in any way that’ll really matter.
If I was forced to give out about something in the E71 it would be the camera. I don’t know if that’s going to be important or not!! The camera is relatively poor compared to other phones in its class, and the video maxes out at 15fps QVGA. Having said that, I don’t see any evidence to say that the E75 will improve on that, although the Video is VGA, not QVGA.
To be honest, if the camera, and/or video are important, I’d go with the E75, however, if these are not the deal breaker, I’d most certainly go with the E71 without hesitation. I’ve played with one fairly extensively and do like it.
If you want to get some more opinions or specs, I think you’d be better off looking at the following links to get a fairly honest opinion, not Nokia’s own opinion. I use these all the time…
You can get a great comparison on features of both phones here.
The E71 with user comments here.
E75 with comments here.
And, a fairly detailed review of the E71 here.
Hope this helps.