Re: garage subpanels
If I understand your question correctly this is the way I look at it.
Is price important since a panel with a main breaker is more than one with main lugs but that depends upon how many branch circuits in the subpanel. If you are out to save a few buck and can't afford a sub panel with a main breaker you may not need one anyway. I assume that you're a qualified person and are familiar with safe electrical practices and procedures and are aware of what you need to do to feed this subpanel from the service entrance per NEC art 250.32 and when a EGC needs to be included with the L-L-N conductors feeding the subpanel. Also, if you should isolate the neutral from the ground bar and when a ground rod is required the neutral and ground bonded together.
But, other than cost, with a panel that is located remotely from the main I like to spend the few extra buck and get a main breaker panel. If you feed the panel from the main with a 60AT breaker and the subpanel has a 100AT main, no big deal as the 100AT breaker acts as a main disconnect and really serves no other purpose.