I think it really depends. I use TOS. My commission to buy 1 contract is $1.5.
Assuming the spread is $0.10, I have to pay 10+1.5+1.5=13 for each contract.
If I buy 100 stocks, I will have to pay $5 in commissions (each way) + about .2 cents in spread, which is =$12. This is slightly less...