I will analyze these two tiers by THREE categories: Movepool, Types, and Abilities.
First off, movepools. I personally think that OU has a slightly better movepool coverage than Ubers, because Ubers consists of almost all the dragons in the game, a bunch of psychics, and some steels. Ubers does not have this coverage, but makes up for it with insanely powerful Pokemon. (Just look at Deoxys-Attack use Psycho Boost with a White Herb. Pure nightmare.)
MOVEPOOL RATINGS:
Ubers - 3/5
OU - 4/5
Types are next. Wow, OU outperforms Ubers by a LANDSLIDE on this one. I can GUARANTEE you that there is EVERY SINGLE TYPE in OU, and only HALF that in Ubers (Arceus's forms don't count, and no megas in Ubers to change up typings). As I aforementioned, the 2 main types in Ubers are Dragon and Psychic.
These 2 types are easily checked and countered by almost any OU pokemon with some form of move.
TYPE RATINGS:
Ubers - 1/5
OU - 5/5
Abilities are last. On this one, Ubers DESTROYS OU. Going to switch into Smeargle and use Sunny Day to boost your Talonflame's Flare Blitz? Nope. Rayquaza comes in with Air Lock and eliminates Smeargle's Sunny Day and obliterates Talonflame with Thunder. You think you can use your Mega Blastoise's Rain Dance to boost the power of your Kyogre's Water Spout? Nope. Same threat. Rayquaza comes in with Air Lock and gets rid of the Rain Dance, and checks both Mega Blastoise AND Kyogre, all because of that amazing ability. You think that your unstoppable Ferrothorn wall will hold out? Genesect comes in, download raises Sp. Atk, and it uses some special fire move. Dead.
ABILITY RATINGS:
Ubers - 5/5
OU - 2/5
OVERALL RATINGS:
Ubers - 9/15
OU - 11/15
So, overall, OU is the better way to go.
First off, movepools. I personally think that OU has a slightly better movepool coverage than Ubers, because Ubers consists of almost all the dragons in the game, a bunch of psychics, and some steels. Ubers does not have this coverage, but makes up for it with insanely powerful Pokemon. (Just look at Deoxys-Attack use Psycho Boost with a White Herb. Pure nightmare.)
MOVEPOOL RATINGS:
Ubers - 3/5
OU - 4/5
Types are next. Wow, OU outperforms Ubers by a LANDSLIDE on this one. I can GUARANTEE you that there is EVERY SINGLE TYPE in OU, and only HALF that in Ubers (Arceus's forms don't count, and no megas in Ubers to change up typings). As I aforementioned, the 2 main types in Ubers are Dragon and Psychic.
These 2 types are easily checked and countered by almost any OU pokemon with some form of move.
TYPE RATINGS:
Ubers - 1/5
OU - 5/5
Abilities are last. On this one, Ubers DESTROYS OU. Going to switch into Smeargle and use Sunny Day to boost your Talonflame's Flare Blitz? Nope. Rayquaza comes in with Air Lock and eliminates Smeargle's Sunny Day and obliterates Talonflame with Thunder. You think you can use your Mega Blastoise's Rain Dance to boost the power of your Kyogre's Water Spout? Nope. Same threat. Rayquaza comes in with Air Lock and gets rid of the Rain Dance, and checks both Mega Blastoise AND Kyogre, all because of that amazing ability. You think that your unstoppable Ferrothorn wall will hold out? Genesect comes in, download raises Sp. Atk, and it uses some special fire move. Dead.
ABILITY RATINGS:
Ubers - 5/5
OU - 2/5
OVERALL RATINGS:
Ubers - 9/15
OU - 11/15
So, overall, OU is the better way to go.