Hate to follow suit but personally also think that the size of the vessel you're thinking about is not a problem. Apart from running costs being higher than for a smaller boat, only mooring could be considered more difficult - but if you don't have much experience - same difference, just get good insurance!
Given the choice I'd also go for the Endeavour, but why take a 43' ketch when you can get a Endeavour 42'/44' sloop/cutter for the same money?