Something to consider is if the pack is labeled as HV which means they are overstating the capacity. If you charge the pack at 8.40V then it will offer considerably less capacity than a pack marketed under standard voltage ratings. There is a belief that HV packs will tend to hold higher voltage (punch) throughout the full discharge cycle.

Without doing discharge graphs under load from equally new packs that haven't sat on the shelf for extended periods of time, it will be impossible to judge performance on any brand of battery regardless of their stated specs.

Buying a pack based on weight alone is not worth it if the pack can't deliver the punch you need. Static weight doesn't impact performance nearly as much as rotating mass, that's the area that needs to be highest concern for stock racing, more info here on gains realized reducing rotating mass:
https://www.rctalk.com/forum/threads...on-4wd.136992/

More info here on battery testing performance:
https://www.rctalk.com/forum/threads.../#post-1368906

Reading that article I can not say the temp differences only comes from the weight difference. The grip of the tire has also a huge influence on the used power.

That's a very good point, because the thinner front 2WD wheels definitely had a pinch less grip and that certainly compounded the gains in performance overall that I saw, thanks for sharing that!

Thinking of reducing rotating mass, what about a thin spur gear similar to the thin pinions? Does anyone make such a thing?

I don't race 1/10 anymore, but it was common to see all kinds of lightening around gears, drive shafts, etc but the most significant gains I have ever seen are selecting the lightest brand tire/wheel you can find... also can reduce more weight shaving plastic from wheels than any other part of the car. Another massive gain in performance is Aura style ceramic bearings with a metal shield on 1 side and you remove the rubber seal from the other side. Then there are tons of high performance bearing oils where the better performing oils need to be flushed and re-applied more frequently to get better performance which is typically faster acceleration and lower temps which improves efficiency and longer lasting punch with the battery, etc...

Removing plastics from wheels is more for bringing in more flex that does provide more grip.
For stock racing you can find smaller spurs but most time they need to be used with larger pinions because the large diameter of the motor requires a certain choice of pinion and spur for the hart to hart distance of pinion and spur. But have people ever thought of the influence of the gyroscopic effect of high revs motor and spur gear on the handeling of the car?

Shaving plastic from wheels is illegal under every ruleset I've raced under.

After flipping through the ROAR rule book, and not finding any such rule, you must not have raced a ROAR event.

+1

ROAR only has max wheel dimensions, I confirmed this with ROAR and this is why we are seeing "slim" wheels and newer designs of tires that remove front foam inserts and also seeing custom 3D printed inserts for the rear which are lighter than foam too!