Q:

Debian Jessie or Raspbian Wheezy for Raspberry Pi 2

I wonder whether I should install Raspbian or normal Debian Jessie on my Pi 2.
Since Pi 2 has a ARM Cortex-A7 CPU it does not depend on the hard float modification anymore. This means, I could simply use standard Debian Jessie without any performance loss, right? I hope firmware and all drivers will be alright, too.
Does anyone have any experience?

A:

Since Pi 2 has a ARM Cortex-A7 CPU it does not depend on the hard float modification anymore. 

It never depended on it.  The SoC has hardware floating point registers; not all ARM processors do, and those systems require libraries and executables compiled to perform equivalent operations using software.  Hence the "soft" and "hard" -ware versions.  You can use either version on a processor with hardware support, but using soft float will be slower.  For the first little while after the pi came out, I believe there was no ARMv6 hard float distro around, hence the first versions of Raspbian were soft float (I think there was already a Debian ARMv6 soft float, and Raspbian was an adaptation of that).
In any case, all Raspberry Pi models can use hard float binaries and that is what is preferable.  Debian has a generic ARMv7 hard float distro and presumably it should work on the Pi 2, since Fedora does.  Note that it will not work on the ARMv6 A/B/+ models, which is mostly why there was a need for Raspbian.  Note also that you cannot use regular x86 Debian on any pi.
The advantage of using a pure ARMv7 system would be that it should perform faster; since ARMv7 is backward compatible with ARMv6, Raspbian will work on the Pi 2 but does not fully exploit the hardware.  
As to whether it is all that significant I don't know; this set of benchmarks make it look ambiguous, except for the SunSpider test at the top.
The disadvantage would be that you have to install your own kernel (the generic one will not work), install the pi-specific firmware, set up the filesystem, and deal with pi specific software and libraries (such as openGL stuff) yourself.  This is not that hard if you have sufficient grasp of how filesystems are structured, how libraries are handled, etc. That guide to using Fedora could be used with Debian as well.

