Ive had both, and the tk is a solid board, and has beautiful backlighting. The only issue is that the bottom row is non standard,so if you are looking to buy any gb keysets, you will need one with a 6.5x/u spacebar, which is hard to come by.
Otherwise, every other key is replaceable, except the arrows are taken up by 0, 00, ., and 2. instead of 2, 4, 6, 8 like usual.
The QFR is probably the most common mkb and is very light compared to the tk. It has a standard layout and is extremely cheap. If anything, you can get one used to try out.
If you use a numberpad alot, the TK is a good choice if you don't plan on switching out the spacebar, or are ok with a limited amount of choices.