Is a 20 W halogen more effective than a 20 W flourescent light? I don't know much about halogen lighting, so you'll have to excuse my ignorance on this.
The best a Quartz halogen light like you speak of can hope for is about 17 lumens per watt.
Common FL's yield 70 and some powercompacts yield 80+ lumens and up per watt. So you get about 5-6x the light for the same amounts of watts vs the halogen lights but you can use them just fine. Search QTL or Quartz Track Lighting here.