Lesser weight will only benefit you. It will improve acceleration, fuel economy, braking, cornering, pretty much everything. Improved tires would also help MOST of these.

improved power will improve acceleration.

Why is the elise able to run with so many of the world's supercars while only having 190hp? power to weight ratio.

 

yep, the underweight car would have a small advantage.

but to keep it in perspective, unless the weight difference was huge (hundreds of pounds), the driver would be a bigger variable than the car.

also, you could always throw better tires (R compound for example) on one car and gain a lot more advantage than you lost by just going with bolt-ons/FI instead of weight reduction. on tight tracks, i'd think R compound tires would make more difference than a 10-20whp (or equivalent wieght drop) advantage.


and one last thing--like was mentioned before, doing both (drop weight + add power) is best, but here's why:
if you start with:
P/W = 100/100=1
when you drop weight to 90 and add power to 110, you get
P/W = 110/90=1.222
so you improve by 22.2%.

but if you add them independently, you get:
add power:
110/100=1.10
10.0%
cut weight
100/90=1.111
11.1%
if you add the differences, you get
10% + 11.1% = 21.1%

which means you'd think you only gained 21.1%, but you actually get more (22.2%) advantage because of the interaction. (i think) that's what he meant.

 

At the root of our DNA is Colin Chapman's obsession with light weight. “Simplify, then add lightness”, he said. It was his philosophy, way before 'minimalism' became fashionable. “Adding power makes you faster on the straights; subtracting weight makes you faster everywhere”, was another of Chapman's premises.