Ok, been running some tests in the cars at Suzuka East (full downforce) and Monza (min downforce). Here is the data I collected. The times for the tracks are in seconds, so for Monza, 108 = 1'48.
View attachment 291430
At the specs on the table, I have an average gap of 0.113 from Fastest to Slowest. They all accelerate at a very similar level and reach the same top speed, give or take 2mph. (tested them all at Route X with default setups, downforce set to the mid-point)
Now, I would say these specs are good enough for a race test in pre-season #2. But, as the data is only from myself, it isn't 100% accurate as certain cars don't suit my driving style, and some setups are better than others (I tuned all of them but I'm not spending hours tuning them all properly), also, its only over two tracks, so testing at more will give more accurate results, and testing with more drivers with different skill levels.
But anyway, these are just the results I collected, do with them what you will.