After thinking about this I think there are 2 best racks.
If security is what you're after then the Extreme is the one you want. It has it's shortcomings though, especially if you don't get the optional engine supports.
If you only need enough security to keep opportunistic thieves at bay, then the TrimmerTrap is the best. TrimmerTrap does a very good job of holding your trimmers without snapping the heads off, the trimmers don't spin around in the rack, they're more affordable than the Extreme and you don't have to add weight to your trimmers to use the TrimmerTrap.