ฉันรักแปลIt just feels like Russian has far more play to it: it's more flexible and more expressive.
The main thing people miss coming to English from Russian is controlling word order. Thanks to declension, we can often reorder the words in even a simple phrase in three or four different ways while preserving the meaning. This is a bigger deal than it seems. In English word order is something that rarely matters; in Russian, it's an omnipresent extra layer of communication, a bit like body language. We can craft sentences to shed light on one part or another, or just to have the exact rhythm and cadence we want.
Cadence is something I feel more strongly in Russian. Getting a steady rhythm of stressed and unstressed syllables feels more natural. It's subtle, but it completely changes how sentences sound, which leads me to enjoy listening to Russian more than English.
Another strength of Russian is how synthetic it is, at least compared to English. Given a single Russian noun, we immediately get a dozen variations on it, with, at the least, a few diminutive and augmentative forms. We might not have as many different synonyms for any given word as English, but we can often convey similar shades of meaning by building up different words from the same root.
A visceral illustration of what this means is how the two languages admit nonsense. With Russian, prefixes and suffixes are so systematic that we can follow the meaning of a sentence pretty closely even if all the roots are made up. We don't even need to use too many "structural" words like prepositions since that information is instead conveyed by the endings of words (ie conjugation and declension). With English, we'd need more existing words to act as signposts.
In the end, this doesn't have much of an effect on me. I still mostly write in English. The main difference is that I find Russian poetry a lot more engrossing than English poetry—but how much of it is due to the language and how much just due to a few uniquely brilliant Russian poets (Khlebnikov, Vvedensky, Kharms)? It's a bit of both, really. On the one hand, the Russian avant garde is a movement that fits my sensibilities better than anything I know in English; on the other, I still prefer Russian even with less deep poetry like song lyrics.