The T:2013 timeline is the weakest part of the game. This is fine with me, as I often go off-canon anyway. (Less NA in T2K, more NA in T:2013)
As far as rules go, T:2013 is a very tight, accurate rule-set that I would use for any modern military game. The character creation and development process and combat rules both stand out to me as the
best I have ever played. Once I became familiar with the rules, the combat sequences in T:2013 played out in a smooth realistic manner in regards to physics and psychology. In addition, every combat ended up having at least one of those cool little dramas that are so memorable.
I love T2k, and nothing will ever replace the feeling of this wonderful rpg, but as far as solid rules are concerned, T:2013 is top. I wish I had more time to play either of these games.