On balance I think having a monarchy beats having a president - but that is solely dependent on who inherits the crown - as someone said upthread, it could have been a King Andrew (I know succession-wise it would not be, but I am sure you take the point.). So Charles is a better bet.
But he will have to think very hard about how the monarchy functions and what it costs. I know that the expenditure on the monarchy is recouped to some degree by the tourist attraction, so we don't really want him in jeans - but I sometimes wonder as I watch these people dressed up in archaic costumes and repeating words from hundreds of years ago if that is the image we want to project of our country.
Charles will have to slim it all down and recognise that some people feel uncomfortable about that expenditure when families are facing the "heat or eat" choice this year.
I recognise that he has done some good charity work - and more of the same would be great - using his high profile for good. But he has also made some dreadful mistakes in life (as we all have) and he must not be deified. He is a fallible human being as we all know only too well.
I wish him luck in his new job and hope that he will set about modernising the monarchy, as other countries have succeeded in doing.