Hey I know your from the UK so I guess your referring to Base? If so it depends on the actual speed itself. Alot of base you get is fucking brilliant for bombing but when you snort it, it does fuck all due to the fact it's all claggy, like tooth paste sometimes. If you cut your base with some glucose or leave it to dry out for while and snort it, you should find that you absorb alot more per dose.
For example if you cut a 1/4 a gram into one line and you squishes 1/4 gram into a bomb and necked it, the line would probably fuck you up more intensly and have you wizzing off you tits, although the bomb would creep up and you have you tweeking for a while longer but less intensly (IE, not rushing and running around collecting diry plates and hoovering the stairs at such a rate)
I'm pretty smacked out at moment and I'm goin off the point, infact I'm not sure what the point was. Hope I answered you question a little bit.