Poker Calculators

[filmsimon]

Hi,

I was wondering if anyone has any advise when it comes to choosing a poker calculator or if there is any good sites that reviews some of the poker calculators and which ones are the best?
I'm looking to buy one and have seen many but no where seems to compare them to distinguish the good from the bad.
I've seen one's called magic holdem, calculatem pro, poker indicator and holdem genius that look quite good.

Any advise would be great.

Cheers

Simon