How would you compare the Maclaren Techno XT to the Maclaren Atom?
There is one, most important difference between the two (even if they might seem similar from the pictures) - the Maclaren Techno XT is a mid-size, umbrella-stroller-style stroller, meaning much more seat space but also a larger stroller after folding... and the Maclaren Atom (read full review here is a travel-first, occasional-use ultra-compact (read more about ultracompacts and what they are and aren't good for in this article).
Unlike many umbrella strollers, the Techno XT is a better-built, more quality stroller, meaning it should last you longer, but it is still very long after folding (and not as study as a single-handlebar strollers). The handle of the Techno XT is adjustable, which is nice, but also two-handed, which can be a bother at times.
The Atom is, as I already mentioned, smaller - smaller after folding, smaller and more slanted in the seat, and with smaller wheels. It is a nice stroller but not, primarily, for everyday use. For such, you'd be probably better off with the Techno XT, as it is a much more comfortable stroller for children, especially as they grow older.
The Atom, on the other hand, is the better choice for trips, traveling, taking with you to visit grandparents - simply better as a second stroller, occasional-use stroller when folded size is the most important thing - more important than the roominess for your kid.
Both strollers boast quite a nice ride in the city as well as very nice canopy size, so there, you'll be happy with them both. The atom, also, has a very breathable seat so is a more suitable 'summer/holiday' stroller.