The Extra platform offers you two options for a bike - one for full-blown enduro and one for pretty much your local trails where you like to go hard. If you like to make visits to lift-assisted trails every so often but only want one bike to smash out your local trails, the Extra and Extra ST are the same frame but with the linkage swap, you can change the rear travel from 135mm to 160mm. It also uses the same shock stroke, so there is less outlay if you do need to change travel.
If we take the ST and put on a 160mm fork, combined with the light 2,200g frame weight, you can cover some serious ground and have a bike that will handle bike park sessions. The ST gives you more pop and fun, and if you like to play a bit more for style points, then the ST is a nice option. If you are a smasher and you know who you are, the long-travel Extra is going to be a better choice. It's got more rear suspension for those "oh sh1t" moments and will not dislike your aggressive attitude when you try to break the rocks underneath you.
Arc8 has worked with CERO engineering (they're behind the Spanish-made Unno brand), and you can definitely see some traits carried over to the Extra. With fairly neutral anti-squat through the range of travel, you will get a bike that does not jack your pedals under load, and with any of today's modern shocks, it will pedal well - there is really no need for excessive anti-squat in your new-age MTB. Take the 64.7º head angle and progressive rear suspension that does allow a coil shock, and you have a bike that will eat up very rough terrain - you could call it enduro depending on how fast you are going. There is no doubt the Extra carries the versatility to be a one bike for all.
There is room for a 500ml bottle, something like the Fidlock or a sideloader is what we recommend