Should there by any reason to ever connect two physical links from single firewall to dual 6500 chassis for redundancy. Or a single physical link is sufficient as the redundancy is attained via firewall failover i.e. connected to the second 6500 chassis.
If you have the following assumption "that single chassis can take complete load of the network/application" then it really isn't going to make much difference to you.
With HSRP failover affects every client whereas GLBP failure of one router does not necessarily affect every client.
And if you want to use both 6500 switches as gateways for different vlans then it requires additional configuration for HSRP.
Having said that if you are more comfortable with HSRP and it is more straightforward i don't think any advantages of GLBP outweigh this - i would use HSRP. This in contrast for example between a choice of RSTP or STP where i would always go for RSTP provided it was supported.