SpeedBrakes significantly mitigate the potential for inadvertant shock-cooling, without trying one's patience. They will also quickly correct the occassional lapses in planning. I would get the SpeedBrakes.

One of the common mistakes I see with pilots transitioning to faster aircraft is slowing down prior to conducting an approach or entering the traffic pattern. Speed brakes can control this problem. When I first trained with an aircraft with speed brakes my first reaction was, why don't all aircraft have these as standard equipment? If you have them, use them as part of your routine flying. If they are not on the appropriate checklists, add a line for them.