The Devilflyrant (my current preference) works well for taking out landspeeders and the like which is an issue for a 'stealer heavy list. He also keeps up with your horde providing emergency synapse so you can avoid those annoying pinning tests and provides useful distraction even without ST.
I really don't get the whole LW/BSw combo. Taking away one CC attack doesn't mean much if the opposing model only has one, the Catalyst isn't so useful with the high Initiative of the 'stearlers. Although a Walkrant can provide good cover fire, I prefer to use 'Fexes for that role.
It comes down to preference, and what weaknesses the rest of your list has. If you can deal with landspeeders some other way and ICs are your bane, the CC Flyrant is the answer (although a souped-up BL can do this too). Will your group allow you to proxy to try them all out?
Failing that, magnets are your friend.