The Bamboo 5k and Rika 5k are very different, but then again, I've not seen two of any different brand or series of stone of the same grit be the same.
If you are looking for a polished edge, you probably want something up in the 8k plus range and something not muddy, maybe a shapton glass stone. It should be said though that 8k edges are only really nice when they are fresh. As soon as they dull a little, there is little to bite into the food and they feel extra dull.
I think the best thing is not to over think it at this stage. Just get something good like the Nubatama set and use it for a while. It will give you some reference points. Once you have those you can say you want sethingn softer, harder, shinier, toothier relative to what you have. In the end you will have a great selection of stones and will have a blast.
It should also be pointed out that sharpening tequnique makes a huge difference to how a perticular stone will work.
Freehand sharpening is far more of an art then a science in my opinion.