Either method can work but obviously you have to fully understand what the autopilot is doing, and what it is not doing.
I often fly off airfield letdowns, i.e. non-precision approaches. I find it more intuitive and more accurate to let the airspeed hold do it's job and to initiate and subsequently control the ROD with collective.
At MDA (actually just before) I level off the aircraft using collective. It helps to know the required S+L Tq setting for the IAS being flown but this was already in use at TOD, then I activate "ALT" hold mode. That way the IAS will not decrease under influence of the AP. If I am visual, I then disengage the Alt and Heading modes together using the release button and fly with all AP modes out. If not visual, with the ALT mode engaged, lowering the lever again will cause the IAS to be decreased.
I prefer this method because levelling off using the VS mode requires hand swapping on the cyclic at a critical stage (to reset the VSI bug to zero). This is in addition to raising the collective to avoid a reduction of IAS as the aircraft levels itself off.