In The Sims 4, you can only travel between communities and neighborhoods by selecting them on the map. Locations are more repetitive, with fewer activities and lots to explore. However, these flaws bring one epic improvement – the game runs incredibly smoothly. When The Sims 3 requires long loading times and high-end computer to play, always
Simp4Sims Overhaul 01 - Sims Graphics Rules this is a config override file that will make your game look better, it will reduce stutter/lags caused by LOD switching, and it fixes several graphical bugs/issues (costs about 5 FPS but greatly improves stability/smoothness) Simp4Sims Overhaul 05 - Cache Cleaner this is a script for a 3rd party
Get Together, one of the earliest Expansion Packs released, offers the ability to form groups, go to nightclubs, and not much else. While the world of Windenburg is a beautiful one, it doesn't justify the $40 price tag on its own. Future expansion packs for The Sims 4 have put in much more content than Get Together appears to offer.
One more thing to consider is that The Sims Freeplay has a rating of 4.2 stars on Google Play, but The Sims Mobile only has a rating of 3.9 (as of September 26, 2019). Even I would personally say that I like The Sims Freeplay better. So as a short answer to this question, both games are actually pretty different.
If you want the more updated software and more mods/cc I’d go with Sims 4. The graphics are also really good & if you get multiple packs there is a lot of content. The clothes and styles in Sims 4 are also generally more modern whereas in Sims 3 you will be stuck with 2000s styles. The CAS and Build tools are also much more detailed in Sims 4