Joined: Jan 2010
Posts: 9,813
Likes: 1,790
From: Northern California
Bikes: Cheltenham-Pedersen racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
It totally depends on the brand, model and production year of the frame.
As indicated, all but the main tubes are of some presumably lesser-quality tubing, but usually this only implies heavier tubing, not weaker.
If anything, the non-branded tubes are likely stiffer and more dent-resistant.