The 420 is the only
way to go – bigger brakes, quieter inside, more subtle suspension, nicer interior, lots more giddy up and so on. It’ll cost a little more for tune ups, but you get significantly improved performance in virtually every measurable way for the bargain.
Plus, if you wanna toss a few $$ to increase performance further, there are lots of simple bolt-on options. On mine, adding only a 500E front sway bar and slightly over sized sneakers added cornering stability, cut down wheel spin and removed half of the body role. Next project is a 500E rear sway bar and HD shocks all around, and the car will have about 85% of the cornering prowess of my former Porsche. Even though you can bolt the same parts on to the 320, the comparatively anemic 3.2 6 banger engine will never deliver the way the 4.2 does.
And fuel consumption – mine gets about 26 mph on hiway trips and, well I never pay attention around town, but would guess 18-20 is typical
Get a nicer toy and you will never regret it.....