Adrio: Having experienced really bad old ones, decent old ones, and most recently nice new 72 spoke Daytons, I say go new if you can. If you must have wire wheels (I must - I put them on my TR250 since I think they look great on the Michelotti body) it is money well spent, IMHO.
That said the next choice would be used ones from a nice dry climate, with low miles (as if you could really verify that...). My previous car, a 69 MGB, came from Arizona and still had its original wheels which were exceptionally clean and tight, but they did start to show their age as the splines were starting to show 80K miles of wear and tear. If I had kept it I had planned to replace them with chrome wire wheels.