That competition sounds great, the likes of City have Mahrez, Sane, Bernardo Silva, Sterling, De Bruyne, Silva etc as possible options in those positions, so I don't see an issue with the options we have, especially since the likes of Sissoko get gametime and Lamela regularly starts for us. The season is long, the sides who win trophies have that depth, we need players who can cover if the likes of Eriksen/Son get injured. Currently we have options who 'do a job' but don't offer anywhere near the same kind of quality.
We definitely wouldn't sign both, I think we've moved on from Martial now and to be honest I'm glad. I'd prefer Zaha, though I personally doubt we'll get him because Levy will baulk at the kind of price Palace would demand and we aren't in a strong negotiating position.