SO which is better for the each-way bettor in a big handicap: 1/4 the odds the first four places or 1/5 the odds the first five places?

Take a 16-runner handicap in which every one of the horses has an equal chance of winning. Say there is no bookmaker’s margin – unlikely in reality, of course, but good in theory for simplicity – so each horse is priced up at 15/1 in the win market.