Van Statten does show himself ready to sacrifice unlimited numbers of his own kind as long as his own survival is guaranteed. Goddard says 200 have died, and van Statten is finally swayed by the threat to his own life, not to the entire population of Salt Lake City. So perhaps the Doctor senses that van Statten is as capable of genocide - even of his own race - as the Dalek, he's just less honest in admitting it. So he's worse because he combines genocide and hypocrisy.

I was one of those who would have liked the Dalek as a Companion, or at any rate a temporary alliance between Doctor and Dalek to escape van Statten's clutches before they resumed their own duel. But I suppose, apart from his previous history making it impossible to work with a Dalek, the Doctor's thought is that the Dalek's personal potential for destruction is greater than van Statten's, in the immediate future at least, and therefore it must be stopped at all costs, even if that means a temporary alliance with van Statten before resuming that duel.

Though I did also toy with the idea that the Emperor could originally have been van Statten, in a peculiar result of his mindwipe, or Adam, who has connections with both the Dalek and Satellite Five. Haven't worked those out in detail though.