The Xbox One fails at multitasking.

At Xbox 1's Launch, Xbox 360's UI was faster for sure. When Windows 10 like UI, rolled out on Xbox 1, it's UI is clearly faster than Xbox 360. Stuff I love about Xbox 360's UI is the Social page which shows you and your friends avatars, and being able to
see who's in a Party without joining it.

I've had Xbox 1 since launch, and at launch, the UI was so slow it was just sad. UI performance is down to like two things. (1) How they make the software (2) your internet speed. I have Vodafone NZ which does 100mb/s down and 10mb/s upload speed. 2 years
ago my house was on ADSL which averages only 7-14mb/s down and 0.9mb/s upload speed. Many people like to share Xbox stuff on YouTube, and I can tell you it's a pain in the beep uploading at ADSL speeds since it's one obvious area ADSL struggles with, compared
to VDSL, High speed cable, and Fibre broadband. Cable and Fibre support like 10mb/s upload depending on your ISP.

I have seen some mention about side bar lag. But bear in mind that the Side Bar menu does interface with online stuff like friends messages etc and if you don't have fast internet, that may contribute to the lag. But it is a Microsoft product so expect to
get regular Updates for it just like they regularly update PC OS's pretty much on a monthly bases. A majority of PC's out there today do run a Microsoft operating system. Rumour has it Sony PC's have one too lol. But Windows 10 (like) is a faster

www.xbox.com/.../experience and personal OS than the previous Windows 8 like UI which Xbox 1 had. They add stuff, find out it's lagging the system too much, and later make performance improvements. Vista was a total resource hog. Windows 7 not so much.
Windows 8 introduced a UI which didn't let you change the dash background and was like filled with a bunch of 4 by 4 boxes no start menu. Windows 10 brought back that personal thing and increased speed.

I can have several apps, maybe even Netflix or YouTube open, and run a game. Sometimes I try to uninstall stuff and the UI doesn't respond. If you have friends with an Xbox 1 console who live near you, go to their house to see if their experience is better.
Or try hard resetting both your console and your internet router. I got a new HP 15ab222tx last year with 6th gen (latest from Intel) Intel Core i5-6200u processor 8GB RAM and Windows 10, I checked in task manager and when Idle, my PC was using only about
2GB RAM. Xbox 1 has 8GB RAM. It also has an EIGHT CORE AMD Jaguar processor clocked at about 1.75Ghz which is a bit lower than Xbox 360's 3.2Ghz 3 core CPU, although it's a really older processor. So since Xbox 1's 8 core APU and Direct x12 thingy they were
going on about, it should be able to multitask fine, since the more cores are processor has means the easier it should be at multitasking.

 

tbown2 out all three consoles. XB1 only one can multitask easyly. PS4 is more hard to do.