I been considering buying some new top solos for a while now. Right now my main top lane is usually Yorick, but I feel that he kind of falls off late game. The two I'm considering of buying right now are Shen, Xin Zhao, or Jax. Do you guys have anymore better recommendations? I'm primarily looking for tanky sustain champions? Also, is irelia worth it?

Irelia worth it bad laning phase can be shut down once you learn her that's hard to do because you'll kill all squishies mid game
Jax worth it sort a bad early game can't really be shut down to hard once he gets items he just starts rolling
Xin Zhao amazing early game damage falls off mid game if you didn't get kills owns late game as bruiser falls off completely if you went squishy assassin

Jax might nd the best late game scaling champ in the game. One of the few champs I would rather have getting kills than the adc because I think he rolls way harder once he had his core items.

it depends on build IMO, I have seen the tanky bruiser dps champs build straight damage and wreck me early game, but lose to me late game because I focused on a slower atmogs build (Riven v. Riven, for example).

Suprised no-one has said nasus yet

Nasus is the definition of late game solo top. You sit top, and ignore the fact that you're laning against another champ. You farm your q, and build pretty tanky, with some damage too. Once your q is farmed enough, you're hitting 4 to 5 hundred extra damage. You can two hit squishies. The build goes like, mercs, shurelyias, frozen heart, trinity, bloodthirster, and then the last is pretty optional. He's unstoppable late game. Try him.

I say Irelia is worth it because even though she has a weak laning phase and can be shut down quite easily, once you get good with her she will be very difficult to shut down in the laning phase.
Shen is a very good champ because not only does he have a great laning phase, but he can split push easily since he can ult into a teamfight from anywhere.
Jax has an O.K. laning phase, but is possibly the best late game champ out of all the solo top champs.
IMO, Xin Zhao has amazing early game damage, but isn't really a good late game champ.
Nasus may be an amazing late game solo top champ by just farming your Q for a long time, but IMO he can easily be beat and shut down early game, requiring him to stay in top lane and farm for an even longer time than usual to become a monster.
Another good late game solo top is Wukong. Again, doesn't have that strong of a laning phase, but his ult is one of the best in the game. At max rank, it can knock up an entire team while doing 200+120% of his total AD every second for 4 seconds. This is a total of 800+480% of his total AD in damage if you catch someone for its full duration

Thanks for the responses guys. I think I might ending up getting Shen first (split pushing seems very appealing to me). Xin and Irelia are free this week so i might end up trying them too.

Btw what are your opinions on olaf and nunu top?

Olaf is a strong situational top (and has a hell of a harass), he beats strong laners like Irelia but will lose to Kennen/Yorick, etc. Nunu is alright, but I wouldn't play him top. Sounds like his only goal is just to survive by consuming minions, I think there are much better picks.