Well when it comes Switching Cisco is far better than HP Procurve Switches, I did experienced almost all Swicthes, the most promising Switch so far I came across is from Cisco. If you have worked with Foundry Switches you can find some similarities between Foundry and HP Procurve Switches,
To certian extent Extreme Switches are good but still the leader is Cisco Switches.
When it comes to price tag and you want to do simple things for Small or mid sized organizations HP can work well. But if you are having a huge organisation then Cisco Siwtches are the best choice.