I have both full sets of metric and standard, 1/4" and 3/8" drive swivels. They get used all the time at the shop. I bought Craftsman, and filled in them with the Snap~on ones that Sears doesn't sell (5.5 and 15mm 1/4" drive). Once you have used them, you find there are area's that they fit so much better then a short socket on a wobble.
My metric distributer wrenchs were all bought off of ebay, 6 US made wrenchs for $20. Well worth that, but with today's non carburated, and distributerless vehicles, not that often used. (I have seen other mechanics use a crowsfoot, on an extension, or even the wobbles). So you might just get them on a need be basis.
Offset wrenchs, since my combo's are offset on the box size (various brands by different degree's from 5 to 15), the ones I most often use, are the ones for the brake bleeder valves.