Best is a relative term. If you're working with ITX build a small form factor GPU design will be the best option for you. If you've got an atx build, then a large cooler design GPU would be fitting in your build/chassis.
With that being said, please pass on the specs to the build you want to drop the GPU into, like so:
Please also include your location, your preferred site for purchase and your budget for the GPU purchase. Location and site purchase preference plays a role as does budget since regions can and will have limitations in availability of one or more SKU's of cards.