If you have the option of engine bars for your bike then consider them too. I went for the latter on advice from the guy at Triumph, and I've read some stuff online regarding frame sliders that suggests that they can increase risk/damage in some situations (e.g. catching on tarmac and causing a flip, creating a single stress point on the frame, etc).
Notwithstanding the above, I'm sure someone with real experience will be along soon
PS Just to add, remember that you can often get engine case covers too.