I've not switched, but am looking to soon. The way I see it:
Tresiba is more stable than Lantus, so get steadier levels for the day.
It lasts longer, so is more effective on 1 injection a day than Lantus.
However as it lasts longer, it takes more days for changes to stabalise, so if exercise changes drastically day to day it may not be ideal.
You cannot get 'Lantus lows' using Tresiba.
I can use the same pens as my Fiasp (Novopen echo) so easier for carrying around and spares etc (This is obvs personal to me)
Then there's the long standing concern regarding Lantus and causing cancer (although this is unproven as far as I know).