I used 20W one as that's what I had at hand. I've been thinking of getting a good solder station, but frankly I do any serious electronics stuff quite rarely and so I've been getting along with the 20W one so far. Used mainly for soldering adapters with a TTL here or there, cabling and replacing hazardous batteries :-)
The current project I'm onto is putting A1200 into my old Antec Overture HTPC case along with custom made keyboard adapter and ATX power adapter with flipflop circuit for the power control.