I have both TTW and F3 on my computer separately.
By sticking to F3 you maintain access to some of the best quest mods which haven't been converted to TTW. New York the Big Apple, Quest for Heaven series, Cube Experimental, etc. You also get to install wanderer's edition, which is harder to tinker with due to lack of MCM, but more expansive in places. The weapon additions are certainly a great touch which mods for TTW and NV have only come close to.
With TTW, you get all of the improved mechanics of New Vegas, with the added ability to mod back in the stuff that was removed, such as Big Guns and the original repair mechanic. Survival fits right in with the Capital Wasteland, hardcore mode feels more in place than in NV. A lot of your F3 favourite mods have alternatives for TTW, and TTW is, on average, more stable.
I like TTW because there are some NV mods which don't have an equivalent in F3. Convenient Accessories, for found and hand-crafted clothing elements, pouches, armor plates, etc. Project Ultimatum, for tactical solutions to gameplay and non-lethal intimidation solution. Solid Project, for numerous additions to the gameplay, including melee and unarmed finishers, including from stealth. TTW allows you to use a number of mods posted here, including Dragbody's power armor mod, for example.
And, ultimately, access to the Mojave Wasteland is very welcome after 100 hours of DC Wasteland. If you tinker with Project Nevada and install mods that take away your gear at the start of the NV segment, you can avoid being overpowered at the start. And finding Benny's henchmen is much more fun and pressing if your goal is to get back your equipment from them.