It also depends on how you plan to use them. if it is alert on deck, then you can think of a Merlin solution. However if you are planning to do an airborne alert then you don't wanna spend Merlin hours not to mention the maintenance that goes with them...
French Aéronavale carry out the Plane guard with Dauphin, small civvy cab thus saving lots of precious Lynx/Panther(although it's the same cab)/NH90 hours. they even have reverted to the mighty Alouette III for daytime plane guard.