Hi petkow,
I'm owning a N95 and since yesterday a brandnew E71. Also I played a bit with the 5800.
Firstly I do strondly advise you against the 5800. As Nokia's first touch screen phone it's still crude, lot's of Symbian applications won't run on it and I don't like it's form factor at all.
Regarding the N95 8GB and the E71 I would certainly go for the E71. Except for the better camera, the more or less useless accelometer, the convinient media player controls (those that appear when pushing the slider downwards) and the possibility to turn the screen format, the E71 has all the functions which the N95 has. However the E71 has a higher battery capacity, it's way more elegant as it's super thin and is partly from stainless steel (at least the battery cover). The most important reason, why I swichted phones, is the keyboard of the E71, that now allows me writing eMails quickly and convinient. The only disadvantage of the E71 which I discovered so far is, that you need to type phone numbers also on those tiny buttons, which is difficult while drinking and while driving. Also I like the landscape screen format of the E71 way better than the portrait format of the N95. Sure, you can turn the screen format of the N95, but then all the keys are in an unusable position.
Regarding VoIP, that was the main reason why I've chosen a Nokia device over a HTC Touch Diamond 2 and the Android-powered HTC Magic, which I also considered to buy.
Nokia's VoIP-stack is superb and it is highly integrated in the firmware, which means it can run permanently in the background and you can place VoIP-calls from the regular dialer without the need to start a separate VoIP-application, which is the case for any other device I've seen so far.
Voice quality of VoIP-calls is really good, but it depends on the quality of your internet connection. If you're on a congested 3G-cell, call quality may drop, but usually it's nearly perfect. I'm regularly calling through poivy, which is a Betamax brand, too.
Nokia supports VoIP-calls over WiFi as well as over 3G, but it won't work on GSM, allthough EDGE does provider enough bandwidth for VoIP.
The VoIP-stack of the E71 and N95 seems to be identical - so in terms of VoIP there's no difference between both phones.
Btw yesterday I found an application called "SIP VoIP settings" from Nokia, which allows some additional VoIP settings including changing the priority of VoIP-codecs. If you're on a volume-based data tariff it makes sense to place PCMU (G.711 μ-law) PCMA (G.711 A-law) in the last ranks:
SIP VoIP 2.x Settings
There's also a version "3.0", which didn't work on the E71, as it didn't appear anywhere in the menus after installation, only the above worked:
SIP VoIP 3.0 Settings
There are some other minor things, that are better on the E71, but I need to leave now, as my girlfriend is getting angry. So, buy the E71!
regards,
Inquisitor