The low pressure turbo has a smaller bore and spools up faster, and is particularly useful for around-town driving. It has significantly less lag and is very responsive when hauling kids (or a cumbersome AWD system). The trade-off is at the top end: there's a limit to the boost it provides and above 45 mph, the turbo magic starts to wear off.

The high pressure turbo spools up slower (lag), but once the power comes on, it delivers a terrific high end kick. Very useful for passing power and short on-ramps. Though the power comes on more slowly, the HPT-equipped Volvo arrives at 60mph well ahead of the LPT. This is better suited to open-road conditions.

Audi/VW uses a very low pressure, constant velocity turbo in their 1.8T engines. Zero lag time, and instant response from 0 mph. But above 40mph, this package is wheezing.....
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David
1998 S70 T5SE // misc mods (mostly lighting) // red calipers
1992 940 GLE // Hella Micro DE foglights and 170K