I would definitely go Lexus

If AWD matters significantly, it seems the TLX has the slight edge.  Acura seems to focus just a little more on sport and performance than Lexus.  Very slight.

If you are used to Toyota's, the IS is a great choice.  2016 is quite a ways into it's cycle, so the kinks have been worked out.  

Same with the first generation TLX at 2018.  It has been around several years into its cycle.  

With the TLX, since you are getting the AWD version, I don't think you have to worry about the dual clutch Honda/Acura transmission, since you would be getting a 9 speed ZF transmission.  

Tough choice!!!  

If you want more reliability, go Lexus.  If you want more sport and performance, but slightly less reliable, go Acura.

Lexus all the way on that one.

Get an IS AWD

Go with the 2016 Lexus IS350 AWD with the true and tried 3.5L V6 and Aisin 6-speed AT.  The 2018 Acura TLX - if you get the 3.5L V6 has cylinder deactivation which has the potential to wear out/damage the engine over time and it also is direct injection-only so susceptible to carbon buildup (need catch can and cleaning valves - which is more maintenance).  The Lexus has neither of these issues!  Also, the Acura V6 was paired with a 9-speed ZF AT, which is 3 more gears than the IS350 AWD’s transmission.  For longevity and minimal issues, I’d go with the Aisin 6 gears versus ZF 9. On the other hand if you get the TLX with the 2.4L I4 (direct injection only, but at least no cylinder deactivation) it comes with a 8-speed dual clutch transmission.  Again for longevity, an Aisin 6 speed is better than 8-speed dual clutch.  Finally, the Lexus/Toyota AWD system is better than Acura’s.  The overall Lexus quality (including fit and finish) is better than the Acura’s.