I hear ya! The Mojo 3 offers a lot of upgrades over the SL including tapered head tube, boost width spacing, internal routing w/dropper, thru axel on rear, and.. if you're coming from a 9 speed the addition of a clutch derailleur is an amazing improvement with almost silent operation. Of course the 27.5+ versus 26 is the huge change.
The plus tires hook up really well, and so while the geometry of the Mojo 3 isn't as ideal for climbing as the SL, the traction basically makes up for it. Also, even though I was worried the front end would lift on steep technical climbs, it seems okay and the traction and shorter stem seems to make up for the difference (but i'm being very conscious of it to keep my weight forward) . I have a TALAS on my SL, and I often used the low travel setting to steepen the head tube during climbs. I miss that feature since I don't have a TALAS on the Mojo 3, but so far I have been making the climbs without by compensating with more butt-cracking the seat to get my weight forward.
Being able to run super low air pressure is the big benefit, and I was being a bit cocky and let them down to 6psi, and it still rode pretty well but I felt the side walls starting to roll in the corners and under hard breaking -- but still amazing I could ride like that.
I have a large SL, and at 5'9" I was on the edge of medium or large. The Mojo 3 feels a lot smaller in the same size (large) , and the large feels almost small for me with the 50mm stem. I think there may be a general trend of running longer top tube and shorter stem, but also toward smaller cockpits so it makes newer bikes feel smaller. I don't necessarily think the large is too small for me but it just feels small in coming from the large SL and with time I hope to get used to it, but if not I'll go to a 60mm stem and lower my spacers stack.
The more slacker head tube angle definitely changes the steering and takes some time to get used to at lower speed, but at higher speed it feels more confident.
As far as gearing, I ran 22Tx36T on my SL with a 3x setup. I ride a lot of steep climbing single track and used the grannie a lot. My 2x Mojo 3 has a 26Tx42T, which isn't quite as low effective gearing, but it's close. If I had the choice I'd get the 24T small chain ring but it is unclear if that would have even been an option since the XT boost crank seems only offered with 26T. Maybe one day I will replace the rings with the smaller option, but I guess you have to replace both rings together which is a costly change.
Oh, and the bars feel wicked wide for what I'm used to. (I got the riser, which isn't much of a rise so I recommend them over the flat bar). I have ridden between areas where both ends touch trees, so I will probably cut them down by 1-2cm off each end.
In summary, this isn't your old mojo SL by any means. I'd call it 75% of an HD3 and 25% Mojo SL. Honestly the frames between the HD3 and Mojo 3 are not very different, with the same head tube angle and just longer wheelbase on the HD3 to allow for the extra travel. It's the component builds on each that really differentiate the two.
I was likely going to go for the beefier HD3 before the Mojo 3 was announced, but was a little concerned if it was too much bike for what I needed. The Mojo 3 seems like a good compromise that made the decision easier, but it's definitely not the equivalent direct upgrade of the light weight climbing machine that my SL is. As I said before, the Mojo 3 isn't really a Mojo anymore, it's a lot closer to the HD3. If I were Ibis I probably wouldn't have called it a Mojo but if this (geometry, 27.5+) is the trend the trail bike industry is going I can understand why Ibis did it and kept the strong Mojo brand name.
