Pretty much the power output. They both share the 2GR-FKS V-6 engine and all-wheel drive, but the IS 350 makes 311 horsepower, or about 50 more than the IS 300. Lexus seems to have achieved this difference in power with a software tune, as the hardware seems to be identical.

Also, if you are talking F Sport, the 2020 IS 350 will have Adaptive Variable Suspension. IS 300 models don't get that feature.

 

350 F-Sport will also get Sport S+ mode, which will adjust the AVS for stiffer dampening and tighten up the steering / tranny shift points and get the throttle peppier.

Other than that and what has already been said, pretty much the same car.

 

Also the 2021+ have (over the 2020):

• updated interfaces for media/nav (including touchscreen and no more joystick), which I prefer
• updated front, side, and rear styling, (I personally love this and was finally able to buy the car)
• and updated suspension and body rigidity. (can't comment but apparently it is smoother and more quiet)

 

My 300 f sport doesn’t have the memory seats and entry feature, the navigation, sport plus. The power difference really wasn’t that noticeable figured I could do a tune later if needed. Not knowing it wasn’t available. Not huge deal though. The 350 I was looking at was a 18 with 30k on it and my 300 was a 20 with 3000 on it for way less $ so giving up on some features for the newness and savings was way worth it.

 

Since the gas mpg is the same... IF you have a choice between these 2 trim levels....The 350 Fsport is a no brainer...

 

Unless the budget is a concern. At the time I got into my IS 300 AWD F Sport, there were very few 350 AWD F Sport available, and all of them were at least $4k more than mine was. In retrospect, it seems like it might've been worth it to just pony up the money, but 2016-me didn't think so.

You don't notice the power difference in normal driving, I must say, and honestly, my 350 F Sport RWD doesn't feel appreciably quicker than a 300 AWD.