The Tid H8 is supposedly a 10w HT radio. I don't have equipment to measure that claim (I forget what that meter is called). But I will say that I get better "mileage" out of my h8 over my h3. What I mean by mileage is that the radio doesn't heat up as fast. And the difference is ABSOLUTELY noticeable. Even when transmitting on high power.
That said, I don't have difference hitting my preferred repeaters (gallatin, brentwood, brentwood grasslands, & lebanon) with either the H3 or H8. But the H8 just seems to "go for longer" -- that's what she said -- before my signal starts to degrade.
I'll say this. The tone of the speaker on the H8 is MUCH more pleasant than the H3 also, if that matters to you. It's a bit more full and not so thin and sharp. So there's that.