HDFC Mid Cap opportunities is relatively new fund, I have invested in NFO and so far has beeng good performer and got 4 star status very early.
but I believe sundaram mid cap is talk more than hdfc so it should be beter one also its old fund than hdfc .. but the repute of HDFC funds also very signficant.
U can compare both of them for any specific difference and inveest into any one of