The ATI Blue Plus are the bluest bulbs I've seen plus the PAR value is pretty good inspite of it being blue.
The UV bulbs are like a black light, very purple. The Geismans are blue but dim IMO and don't bring out the fluorescence like the ATI bubs do. The ATI bulbs bring a blueness to the tank like blue LED moonlights will but they are BRIGHT! I use my ATIs for sunrise /sunset and also as actinic supp. from my regular bulbs.