Actual output my vary slightly from battery to battery but should be close to the same, even in the same product line there will be some variation. I looked around a little for actual tech specs on both and I don't see anything. Nearly all e-cigs are 3.7V even though they likely come off of the charger higher than that, even up to 4.2V. The biggest gain is going to be from the lower resistance, so to somewhat answer your question, yes it will give you close if not exactly the same effect. If you G6 is getting older and starting to die out, then that won't necessarily be true. Many factors here but the main point is that the lower resistance is you biggest gain given the set-up mentioned.
As for the main distributor, I'm not sure. Redds and Redd E-cig look to be completely independent companies.