"Я считаю Пушкина более талантливым поэтом, чем Блок" or "чем Блокa"?

Here I am sitting late in the evening, struggling with a home test devised by a university teacher of mine, and here is a question in the test:

Как корректно закончить следующее предложение?

Я считаю Пушкина более талантливым поэтом, чем … .

(а) Блок

(б) Блока

The teacher is known for setting up traps and being harsh to students (see, e.g., this post of mine). The test I am currently struggling with is full of nasty traps set up by using homonyms, idioms, double meanings, etc. Some questions have more than one correct answer, and some – none at all. The good news is that I can use the Internet and, in particular, the Russian SE, as the test is to be completed at home.

I tried to find the answer to the above question by doing research in Google, but got very much confused and puzzled. One the one hand, a classic Russian writer, Lev Tolstoy, wrote in his novel Anna Karenina:

– Нисколько, – Левин слышал, что Облонский улыбался, говоря это, – я просто не считаю его более бесчестным, чем кого бы то ни было из богатых купцов и дворян. (Source)

He used the same grammatical construction as the one in the test question and chose either the genitive case or the accusative case after чем, and this suggests that I should choose Answer (б). On the other hand, I found examples suggesting the opposite. Here is an example:

Считаю его более значимой фигурой в игре команды, чем Аксель Витсель. (Source)

Especially confusing is this article. Its title is: "Считаю Жевнова более стабильным, чем Малафеева." But the same article also contains the following sentence: "Но все равно считаю его более стабильным игроком, чем Вячеслав Малафеев." That is, the author flip-flops like a landed fish when choosing the grammatical case in the grammatical construction my teacher is asking me about.

My gut tells me there is a trap. The whole sentence sounds somewhat weird to me, so I won’t be surprised if the teacher says that none of the suggested variants makes the sentence right. I also won’t be surprised to hear that both suggested variants will do the job and can be used interchangeably. And who knows, maybe only one variant is correct if formally judged by some strict grammar rules only teachers know.

So I am curious as to what native speakers have to say and whether they can help a confused Japanese student evade a trap set up by a harsh Russian teacher.

Which variant should I choose and why?