How do you compare chainsets on MTB? Which is better?
You are mixing quality with quantity (on this case gear range).
1x in a true MTB setting gives more than enough range for a majority of riders most of the time. MTBers on 1x tend to elect a chainring that gives the lowest low gear they need for climbing, and accept the limited loss of time that occurs the few times they are spun out at high speeds.  Reality is if a technical MTBer is going fast than spun out speed, they are concentrating on lines, jumps and landings, speed is far from a  priority.  The advantages (listed in the answer by @MaplePanda) out weight the loss of top gearing.
2x is useful for those who ride big hills on roads and need a low gear for climbing and a high gear for high speed descents, or weaker riders than need super low gears for hills. Until recently 2x has also been a viable choice for budget, but 1x is now avaible as some quite low price points.  The 1x fanboys often come with a 1 eyed view of its advantages, most of which suit experianced rider significantly more than inexperiacned riders (eg. Anyone thinking about Altus or SX is not a weight weenie, probably cannot afford a dropper and almost certainly buying a hard tail where there is plenty of room for a front derailluer)
There are many other group set options on bikes - if you cannot find what you like at the price point you can afford, keep looking.
In terms of quality, Deore is (IMHO) the best in the list you have given. Altus is considered too low quality for reliable operation MTB standards, but is suitible for road and occasional light offroad use.  SX Eagle is somewhere close to the Deore in quality - probably comes down to personal preference.