I like the idea of not having to have a fan ... maybe. lol

Orienting heat sink fins vertical and given that warm air flows up, makes the best use of passive cooling. Can you tell that I am an engineer? Apologies. Probably good that there be a little air space around below and above the heatsink. 

On the other hand, the specs for fans include the dB noise level and a very quiet low speed fan can greatly improve heat exchange in any orientation. Just read the specs and investigate.