I upped it to Max last week for two league games against much tougher oppo and battered them both winning 3-0 and 4-0 away from home while not attending the games.

They definitely give you a slightly better chance but it is not as if you were purchasing success.I would guess a max bonus would equal a 5% boost at best. But then there is fitness, form, the roll of the dice and everything else to add to the mix.

If you can afford to leave it maxed out ( I am getting near there with a billion in the bank, then why not?)