35mm. It's more versatile. The 50mm is such an overrated lens not to mention not a good portrait lens.People's heads will get distorted when shot with the 50mm (unless you're going for the distorted head look).
I agree with Peteroc. Keep the 35mm and get either the 85mm or 135mm.
Are you saying the 35mm is better than the 50 for close portraits?
Personally, I think neither is good for that, use an 85mm or 135.
Bodies: 6D, EOS-M
EF Lenses: 35mm f/2.0 IS, 100mm f/2.8L IS Macro, 135mm f/2.0L, 16-35mm f/4L IS, 24-70mm f/2.8L II, 70-200mm f/2.8L IS II; EF-M Lenses: 22 f/2, 18-55
Speedlites: ST-E3-RT, 600EX-RT (x3)