Merlin HC3
As a Mk 3 operator, I can echo the enthusiasm of the RN. Yes, the Chinook can lift three times as much, but the Merlin can go as far, faster, more quietly, more smoothly, in greater safety, better protected and with more, more modern, kit in the cockpit. Our icing clearance is already better than any other helicopter in UK service and that's only at the interim level. Yes, there are things I'd like to chnage about it, but would I swap places with a Chinook pilot? Not for all the 10 ton ISOs that are moved from one end of a car park to another every year!
As for the rumour that Merlin can't hover on 2 engines, I have to suppress a yawn every time I hear it. At max all-up mass, at high density altitudes, if one engine fails, you can't hover; but show me a helicopter that this isn't true for! Actually the OEI performance is impressive. You're often not committed until the very last minute, if at all at training weights in a temperate environment. Think about it: if you lose an engine in a twin engine helicopter, you're down to maybe 60 percent of your power, taking into account emergency ratings of the engine; in a 3-engined helicopter, losing an engine limits you to something more like 75 or 80 percent. And in any case, the RTM 322 is incredibly good - I believe the rate of engine rejection is still in single figures after some 120,000 hours of fleet operation.
Spares are still an issue, but when you have them, this is a very reliable aircraft. The availability rate of the Mk 3 in Bosnia was close to 98 percent.