The dlink doesn't support 3x3 mimo either.
The radio chips these devices use are identical. The CPU is a little different but hard to say how much if any difference that makes. Most difference will be in the software features.
You need to be careful about chasing bigger numbers just for bigger numbers sake. First you nic cards must also support these feature. For example if you nic do not support 802.11ac then it will run like any other 802.11n router. It is not real common to get a nic that has 3 antenna and the speed increase going from 2x2 to 3x3 looks really good on paper but does not work as well in real use. It is bad enough with all the interference today trying to get 2 overlapping signals but to get 3 is even...