Good analogy Dolus.
Anyway, the question of multiple betting or NOT, just comes down to how you select your horses to bet. If you've cracked the secret of which day a certain trainer "is on fire" and he has two in the race then maybe you'll be betting both. Maybe it's an "overs" type thing (you want 100% and today there are 3 or it's only 1 in this race). Or you've decide to bet EVERY time on your top 3 picks regardless of price. Or just the highest rated. Whatever.
If you are betting multiple runners it must be most (or all) of the money (which would then be level stakes) on whichever "type" of horse has proven most reliable, POT-wise. The "type" might be an actual "type of horse" or a "price" How often in this thread have I read that "on the days when shorties come you get ************ all" or "when the fifth selection gets there it's a bonanza" Check your records; are all those shorties (causing your bank to bleed) being subsidised by the longshots which should've had even more on them?? What about "reverse" betting (putting MORE on the longer prices or at least the most profitable price-range) if you can't bring yourself to discard some of your multiple picks?
Say you've been betting a 2-1, a 5-1 and 9-1 chance in each race and dutching (ie $10 on the shortie, $5 on the middle and $3 on the longer). That's $18 bet for $30 return. You notice that for each ten shortie bets you are getting 4 winners (POT 20%), for each ten at 5-1, 1winner (-40%) and for each ten at 9-1 you get 2 winners (100% POT). You should put the lot (ie $18 which is then a LEVEL stake) on the longies from now on OR maybe split it between the shorties and the longies (preferencing the better POT 9-1 shots) but DITCH the middle as those ones are LOSING YOU MONEY. Or if you insist that there MUST be three bets, do it thus $10 on the 9-1 shots ,$5 on the 2-1 shots and only $3 on THE WEAKEST LINK, the 5-1 horses which have been losing 40% for you. Should it continue as before you will either be still getting A) !00% POT on the longies BUT with six times the money on them (if you chose the "whole $18" approach) or B) 100% POT with $10 on them AND still 20% POT on the shorties (but with $5 bet instead of $3).
However you look at it, if you bet multiples it has to be bigger on the MORE, and biggest on the MOST profitable (as seen by your results). Cheers.