Im sure its something obvious
If you find something obvious let me know 
It seems a lot more divergent
now than it used to be.
Texas Instruments has a very good Logic Family brochure that highlights the advantages of each logic family. On-semi may have one too. On-semi is mostly SMD packages for their logic. I am not sure about the other mfgs. I try to use TI and
On-Semi.
Usually you can characterize the families with a couple of specs --
design voltage (nominal Vcc), Vcc range, output drive, and the
most important spec -- 5V tolerant inputs For high-speed applications
you will need a couple of more numbers.
Do not make the mistake of buying the fastest logic. If your system
is not designed for high-speed logic you can get poor performance
due to reflected signals.
(* jcl *)