Tommy was already a teenager and a career Ranger when he received the White Tiger power.
Kou didn't have any powers before the KibaRanger powers, not even the DragonRanger powers. However the actor Hisashi Sakai who played Kou/KibaRanger previously played child Burai in the previous year's Sentai series.
Tommy had Green Dragon powers before the White Tiger powers.
Kou used the Kiba Changer to transform.
Tommy used a golden Power Morpher with the Tigerzord power coin to transform.
Kou was not the leader of the Dairangers.
Tommy was promoted to leader when he became the White Ranger.
Kou's powers were only seen in one season.
Tommy's powers were seen in season 2 and season 3. Although he had different power coins, he still retained the same suit.
Lin, Hououranger (the Pink Ranger), was a mother figure to Kou; and has no relationship with Mei.
Used his Dairanger based powers longer than his Zyuranger based powers alongside his teammates' Zyuranger based powers (this is counting replacement Rangers and their 3rd season ninja powers using their old suits).