Tony Allen had a moronic uncaring of young talent coach
Marcus has a much better coach and caring of his young developing talent
yes, but tony allen was a quinessential bonehead who could jump out of the building and would immediately follow that up by making a profoundly stupid pass or decision. on defense, though they are different in details, tony allen and smart are overall similar - dogged, determined, good. though i think smart is stronger and impacts the game in more defensive dimensions (like the free throw at the end of the cleveland game. allen would not have done that.)
where they differ is #1 brains. smart is smart, by and large. tony allen was not and made a ton more poor decisions. smart uses his smarts more than allen ever did since allen had so few of them. god, how i would sit and be stunned by some of his "decisions" and lack of awareness on the court.
also ball handling. god, i cant count how many times allen would dribble the [dang]ed ball off his foot trying to drive 1-3 to the basket.

smart's ball handling is better, and smart is younger and improving more than allen did. allen was 23 as a rookie. smart was 20 years old.
final point is offense. both have shown to be unreliable 3 point shooters. (careers: TA 28%, smart 29% - but it is too early to decide with smart) though smart right now may be worse.
(but what gets me about smart is that he does make what i see are "big-time" shots in close games.....sometimes. in the game with atlanta he took and made two key 3 pointers.)
allen's offense really came from his ability to jump through the roof. on missed offensive shots he would soar towards the basket and slam back the rebound. he was amazing at that, one of best i had ever seen. then he blew his knee out and that changed his game.
in contract, smart seems to be chained to the ground. on his drives he tries to bull through people, not fly over them. both allen and smart are limited on offense. earlier in their careers, allen was the flashier offensive and stats show that allen was slightly the better scorer. (adjusted for 36 minutes)
but again, allen was older by 3 years when he entered the nba.
so, are they similar? at first glance, yes, very. but if we look deeper we can also see important differences as well.