Khajit gonna give u more damage, redguard - more sustain, orc - more health (u can use 7 medi and be ok with it).
Personally,im playing as a khajit and it is ok for me.
U won`t loose a lot of dps, even if u will be bosmer, so don`t worry and choose,what is ur preference.
I have a Redgard and a Dummer DK. Redgard for PVE tank. Dummer fro PVP mag DK.
This will come down to how you like to play. Orcs are faster and can sprint better. DK's are slow so this is a positive. Redgards have great racial passives for Stam recovery. There are of course other passives, but these are the ones I think of in your situation.
Orc will give the most burst damage on a melee build, but sustain issues cause Redguard to pull ahead in long fights. A stam DK works well with both of these races because the racial passives synergize well with DK melee skills.
You were right to not include Khajiit and Bosmer in the poll. Khajiit performs like a weaker version of Orc (burst, but weak sustain, only better for pure ranged builds). Bosmer performs like a weaker version of Redguard (built for sustain, but only better than Redguard for a pure ranged build).