hard call, really a personal choice... personally I'd go for threadless for better stem options (you might have to use a shim with a 1 1/8" stem)... I assume this bike is for riding so go with the easier to use threadless stem, You can get it higher and have removable face plate etc...
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1 Super Record bike, 1 Nuovo Record bike, 1 Pista, 1 Road, 1 Cyclocross/Allrounder, 1 MTB, 1 Touring, 1 Fixed gear