I saw a BikeRadar video showing a comparison between 2.35" tires and 3" tires. The 3" tires won. Then I read a few messages from people saying they beat their personal records by going 27.5x2.8" instead of 29x2.35".

So, if Plus bikes have an advantage, how do they compare to 4" tires? I'm asking because I did a search on Youtube and wasn't finding what I was looking for.

Won what? Speed, bump smoothness, traction? So many variables. Rider weight, terrain. tire psi and so on. My summer fat bike tires are 4" and usually 7-12 psi. My 3 " tires on the Krampus are 10-18 psi. Add in 16. 17.5 and 29er rimes too. Try this, do some demos, decide for your self on how you ride your terrain. My fatty in the summer on less tech trails wins for the fun factor.

I have a plus bike 27.5x3.8 and a fat bike 26x4 and I've owned a 29er with 2.3s, all hardtails. With my plus bike I don't have to be so picky with choosing lines so I can clear things a little quicker but overall the 29er was just faster. My fat bike is slow but will roll over anything for the most part. If I'm on the fat bike I'm not looking for any PRs. The wider the tire the more traction you get, but you may end up sacrificing speed.

pretty sure there's some sponsorship from a bike company pushing plus bikes in those "reviews"
I'm running just about every size tire at the moment, yeah I'm one of those guys....
And yes, my fatbike will be faster in 6" of fresh snow than my XC bike with skinny 2.35 tires.
I personally don't like 27.5+ tires, but lots of people swear by them but I'll never tell them a 29 wheel is better

I read that BikeRadar test. BikeRadar is one of the sites that I generally trust, but they were pretty clear that this was just a few riders on a few specific bikes and trails. This topic is definitely not settled. Plus tires have not found much success in the Enduro scene and are virtually non-existant in the DH scene.... for the same reasons the idea flopped in the early 2000s (there were many 2.8 DH tires available and even a 3.0).

Even in its most recent incarnation, plus size tires have downsized a bit from 3.0 to 2.8. So the idea that bigger would always be better has not really been born out even in the plus tire niche. Hard to say if the recent 2.6 tires are small plus or large standard.

I don’t think fat tires are ever going to be anyone’s choice when speed is the main criteria except when the flotation and traction they provide is key..

In 2016, plus bikes were plush and forgiving. Now in 2019 they’re allegedly vague and squirmy.

my bike is 27.5 x 2.8 and I it