Xerath's waveclear is on par with any other siege mage, if not the very best of that group. Vel has to use up multiple charges of his W or risk using his E to clear waves, and Ziggs has to use multiple Qs because his E's waveclear was nerfed. Xerath can simply Q+W to clear entire waves as soon as he gets any AP item greater than an Amplifying Tome.
His Q poke range is exceptionally long, and he doesn't have to do geometry like Vel'Koz to get that range.
His W is amazing for setting up and following up on other AOE damage abilities (including his own Q and ult).
He has better mana sustain than his main competitors, Ziggs and Vel'Koz, because of his passive.
His ultimate has a higher damage potential than Ziggs' ultimate and less travel time— in essence, it requires more skill but has greater rewards (though it doesn't really provide the option to clear waves in side lanes from mid, like Ziggs' does). It has longer range than Vel'Koz's, meaning it can reach enemies that are farther out than Vel's ult range and it allows Xerath more safety while using his ultimate (less risk of interruption), though it has less potential damage than Vel's (because of Vel's passive) and it doesn't slow enemies.
If Xerath has any glaring weakness when compared to Ziggs and Vel'Koz, it's his lack of hard CC. His E is quite lackluster, but he makes up for it by having extreme range and AOE without the "contexts" that Ziggs' and Vel's high-range skills have (Vel Q has to be angled for max range and can only hit one target if you use it that way; Ziggs' Q is easier to dodge in general and has "bounces"), plus he has some mana sustain built into his kit.
TL;DR: He's not particularly better or worse than the other siege mages, in my opinion. Less CC, but with easier poke, extremely strong waveclear, and mana sustain.
feel awkward to play to anyone else?
So when the GotS skins came out on the PEB I was Exited. I already owned 
and 
or 
mid instead.
