My Fender Bandmaster (6L6) and my Delta Blues 210 (el84) have distinctly different sounds....I wouldn't say one is "better" than another. It just depends on what you want. Most of the time, you'll find 6L6's in higher wattage amps (e.g., 40 watts and higher) whereas EL84's are used alot in lower wattage amps (e.g., Blues Jr., 30 watt amps, etc.). A nice 50 watt El84 amp is the Peavey Classic 50.

I don't know that one tube is "better" than the other...it's just a matter of preference.