Hey Camox! High quality renders you have here!
My favourite is sure b1, because of the architectural subject I think

It is really well-balanced, as an inner space, AND I'm fond of double heights, so...

I feel it like sort of a wip: seems to be a library or something similar, but there are no seats or places to read. It's like a huge space and that's it. I think that could be really great if you'd be willing to fill the space with some people (...motion-blurred?) and maybe to enrich the lighting. Are you using sun and sky? Try Envmap instead: it could really come out wonderful, with the right map, IMHO..
K2 is interesting too. I like quiet spaces. In this one too I feel there's something missing: maybe a simple glass table on the right corner could do the job.. The kitchen is undoubtfully the main subject f the render, but I like it starring in a more discreet scene, nothing with fancy leds, shiny spotlights all making lots of sparkles around it, like in a showroom or something. This is a great kitchen, which just knows to be great and doesn't have to show off.
5454 is very "pictural", although a little "forced", if you pass me the term..

, 784 is very simple and plain. I like the brick material, and I'm envious of your "fur" system

, but I think you didn't pay the right attention to the floor mat..
It is good work Camox. Congratulations.