I would prefer De Guzman over both of them. Strong all season in the Prem for Swansea, and has some international experience with Holland.
Diame will be off to the ACON every so often which is not something we can afford all the time we have a small squad, and McCarthy just doesn't look as good a player as De Guzman.
http://www.transfermarkt.co.uk/en/de-guzman-eyeing-permanent-swans-deal/news/anzeigen_111452.html
http://www.transfermarkt.co.uk/en/de-guzman-eyeing-permanent-swans-deal/news/anzeigen_111452.html
The two articles suggest that there is a decent chance De Guzman may be available in the summer, depending on whether Villareal secure promotion or not. Ok, Swansea have the inside lane on this one, but you can't tell me the player wants to live in Swansea instead of somewhere a bit more.... cosmopolitan?