[chickenboot]

I always thought that the key was to mash with an appropriate volume of liquor (or 'water' for those that don't enjoy the brewing jargon): if you chuck all the liquor in (full-volume mashing I think it's called), the thin mash means that there's less contact between the enzymes and the starches which I would expect to result in a different chemical composition.

Batch sparging on the other hand (following a mash with a regular ratio of liquor/grain - but rather than slowly rinsing the grains with sparge-temperature liquor, you fill your mash tun with your full volume of liquor at sparge temperature) may affect efficiency (positively or negatively), but shouldn't change the quality.

I've enjoyed some fine batch-sparged beers!

Oh and as for the OP's point about a beer taking three hours... I wish! For me it's more like 8 with all the cleaning and fiddling around in my tiny brewing space!