Do you feel it's better to keep your head coach, since your players know the system and are chosen to play in it, or do you feel you need to change him because your opponents get accustomed to what you do ? What is the most important in your opinion ?
I tend to think the knowledge is a big thing.

well I for one would say that it is better to change him if like a better rated coach is in the market especially if that coach has like made the playoffs awhile your coach hasn't because I would think if you got a better rated coach and that coach has playoff experience it will help improve your team versus a lower rated coach and that coach hasn't sniffed the playoffs at all.

btw you would think if a coach didn't sniff the playoffs with his current team that would be motivation for him to find a better team or at least take offers from teams that have been in the playoffs.

Only way for to keep him is if you cant find a coach who isn't better rated than him or at least that's what I do which to be honest I do both if I can find a better rated coach than my I will try to get him and if I cant find a better rated coach I will stick with him for present moment unless some coach that is better comes free later down the road.

i would say keep the coach so your players know the playbook, if you find others predicting your teams choices too much you can always change up your settings for how often your personell set is called (will change how frequently each play is called so will offset opponent scouting) and change how often each type of play is called on offense (eg. run or pass) (this will throw off an opponents run/pass defensive setting) you can also change up your rules so that your team will act differently than they have in the past, i would say that changing the coach, which basically just means changing playbooks is something to keep for use only if nothing else will work