IMOH the flight instructing is by far the best. Can never figure out why its slagged off... if you read the article in the back page of R. and W. this month you will see Tim McAdams address this sort of stuff.
Yes, any time is better than no time but operating at the limit of the aircraft, making command decisions and building your instincts is of tremendous value. Your handling skills will improve ten fold even if youre not on the controls much. And dont forget that you will be doing those same moanouvers once every six months for the rest of your life so having a good grounding in autos etc is a big help... afterall a SE run on landing in a 412 is exactly the same as the running landings you used to do in the R22. Poleing a 206 in ENG... (which doesnt need to be hugely accurate flying), with someone else making the decisions is better than nothing but hardly of tremendous value.