[citation][nom]lp231[/nom]ULV are nice for their low TDP, but to achieve that, it runs at a slower clock.Out of the 3 mentioned, the i5-3427U and i5-2557M are good choices as they have decent clock speed (1.8GHz and 1.7GHz) The i5-2537M not so much as it operates at 1.4GHz[/citation]
Good enough for regular work. A 2GHz P4 can do more than well enough for regular web browsing and I'm sure that even a 1.4GHz Sandy Bridge CPU can probably at least triple the performance of a 2GHz P4 per core, let alone with both cores in use. Then there's Hyper-Threading to consider that the P4 in question would probably lack or it would have a more rudimentary implementation of it. This would also all be while using far mroe power than the Sandy Bridge. Point is, these CPUs are definitely enough for most work. Sure, they don't hold up for high end gaming and such, but they do more than well enough for what they should be used for.