i would still get the CSL, just for one unique reason, its engine sound....Dont compare the gtr sound vs a m3 csl sound , there is no competition whatsoever.
If you like the sound that produces the wind, then get a GTR
If you want a raw, sporty, throaty sound, then get the csl
Also the gtr for daily driving and parking will be more difficult due to its size vs the csl, which is as big as a normal 3 e46 series....also if you are going to drive with the family, I hope you will park the car in many different parking spaces....can you imagine what could happen if you park a gtr to the public, they are very rare, and in more than one occasion you'll have a little surprise
Oh and what about the price?...Here in Spain, GTR are something between 80.000 Euro , and a good shape second hand m3 csl goes for something like 50.000 Euro ...
and as you are form germany, those prices are even more more cheaper.
for me its no brainer......CSL
oh and if you decide to get that rocket (THE GTR), DONT YOU EVER USE LAUNCH CONTROL
, ( i suppose you know the story with launch control + gtr = warranty avoided + engine failures!!!