I don't mean the reason is one aspect of his work is 'better' than the other, just that the difficulty translating his short stories makes them much less accessible to English readers than the plays.
I think the reverse is the case for Russian - Жалобная книга (The Complaints Book) is part of Russian idiom, the famous play Чайка (The Seagull) is not. Chekhov just occupies a different part of the English-speaking cultural taxonomy.
A (maybe more than a little over the top) way to put it is, it's like if in Russia, Newton was primarily known as a great theologian and alchemist.
Strugatski brothers' Monday Begins on Saturday is aslo a difficult translation from Russian. I really love Russian literature, especially modern writers like Vladimir Sorokin, it's so different.
Anything will be hard to translate between languages as distant as English and Russian, to be quite honest. Monday Begins on Saturday just has more contemporary cultural references that Russian readers understand. Chekhov's stories probably have just as many but they are just as lost to the contemporary Russian reader as they would be to an English translation one :)
On the other hand, I remember watching Russian translation of the Naked Gun and finding it extremely funny even though neither I nor the translator understood any references there so, I guess, it's still possible to enjoy art without the context.
There's a lot more runway, in a novel, to establish style and voice - both for the authors and for the translators. Monday Begins on Saturday begins:
"Я приближался к месту моего назначения. Вокруг меня, прижимаясь к самой дороге, зеленел лес, изредка уступая место полянам, поросшим желтой осокою."
Pretty much ez-mode compared to this opener, in the Gooseberries (Крыжовник) someone brought up upthread:
"Еще с раннего утра всё небо обложили дождевые тучи; было тихо, не жарко и скучно, как бывает в серые пасмурные дни, когда над полем давно уже нависли тучи, ждешь дождя, а его нет."
Two different translators' takes:
"The whole sky had been overcast with rain-clouds from early morning; it was a still day, not hot, but heavy, as it is in grey dull weather when the clouds have been hanging over the country for a long while, when one expects rain and it does not come."
and
"From early morning the sky had been overcast with clouds; the day was still, cool, and wearisome, as usual on grey, dull days when the clouds hang low over the fields and it looks like rain, which never comes."
The ‘Gooseberries’ excerpt sounds close to ‘stream-of-consciousness’ with the attempts to describe the inner mood—and indeed I can't think of anyone speaking or writing in English in the manner of that passage, except Nabokov. As a translator, you'd basically have to imagine maybe John Malkovich narrating your book, and then whack at the words until they sound natural coming from him.
I think the reverse is the case for Russian - Жалобная книга (The Complaints Book) is part of Russian idiom, the famous play Чайка (The Seagull) is not. Chekhov just occupies a different part of the English-speaking cultural taxonomy.
A (maybe more than a little over the top) way to put it is, it's like if in Russia, Newton was primarily known as a great theologian and alchemist.