Thanks guys.

So the general consensus is that, if the prices were the same, then the result would be reversed less more commission due to more winning lays than winning back bets (although then I wouldn't be paying larger commissions on the winning back bets). It's all very confusing.

Obviously it wouldn't be possible to have the same prices but if I have a 10% or less back/lay ratio (meaning the lay price is within 10% of the back price) then the results should only be 10% worse (possibly less commission).