Since English is not my native language I can not decide which one of the following two sentences is better.
- We help companies sell more and consumers pay less.
- Helping companies sell more and consumers paying less.
The first is a sentence and is fine.
The second is a phrase but would be better written as either of
depending on who you are helping.
There is no require for a corporate slogan to be a sentence.
At the least, sentence 2 should read Helping companies sell more and consumers pay less.
And it depends on how you are planning to use it. If this is a slogan for something I would use option 2. But then the logo/name of who is helping needs to be very visible for it to have an effect.
As an explanatory/informational sentence, you can use option 1.