Shell – Who is file owner if the file is created using sudo command

I logged in using my username ravbholua:

ravbholua@ravbholua-Aspire-5315:~$ echo $LOGNAME
ravbholua

I create file named a1:

ravbholua@ravbholua-Aspire-5315:~$ echo>a1
ravbholua@ravbholua-Aspire-5315:~$ ll a1
-rw-rw-r-- 1 ravbholua ravbholua 1 Oct  8 09:57 a1

As expected the above file has me (ravbholua) as owner.

Next I create a2 using sudo with echo command:

ravbholua@ravbholua-Aspire-5315:~$ sudo echo>a2
ravbholua@ravbholua-Aspire-5315:~$ ll a2
-rw-rw-r-- 1 ravbholua ravbholua 1 Oct  8 09:57 a2

The owner is me only, i.e. ravbholua.

Now I create a3 using sudo again but with vim command:

ravbholua@ravbholua-Aspire-5315:~$ sudo vim a3
ravbholua@ravbholua-Aspire-5315:~$ ll a3
-rw-r--r-- 1 root root 10 Oct  8 09:57 a3

Oh! how come the owner changes now. It's not me but root.
Why such variation with echo and vim!
It's a surprise that with change of commands how can the owner of the created file changes.