YouTube user aunumero73 has posted a video showing a broadcast FM selectivity comparison between the rtl-sdr and the Funcube Dongle PRO+ (FCD+). The FCD+ is a software defined radio similar to the rtl-sdr, but with better overall performance. The video shows that the Funcube Dongle PRO+ has significantly less interference when tuning to a weaker radio station right next to a strong local station. Of course the near $190 USD cost of the FCD+ vs the $20 USD cost of the rtl-sdr needs to be noted.
Another comparison between the rtl-sdr and Funcube Dongle is made on this website for signal to noise ratios for multiple tested frequencies .