Life / Best city to commute by bike in Poland ? [4]

What is the most bike-friendly city to commute in Poland out of :

Warsaw
Kraków
£ódz
Wrocław
Poznań

I'm talking about bike lanes , altitude difference and number of people in general bicycle commuting.

P.S. I come from a country where bike lanes are a joke , drivers are considered the worst in europe and the city is full of hills and the altitude goes from 0m to 350meters . So I'm not Dutch and I'm not discouraged easily.

360km of bike lanes/paths for 3.054.678 people
1km for 8.485 people

150km of bike lanes/paths for 1,030,000 people
1km for 6866,6 people

Wroclaw
international.simplerent.pl/uncategorized/sporty-wroclaw.html

Warsaw
polishguide2012.pl/en/warszawa/tourist-guide/show/3197