Is there a Steem node count somewhere?
I don't think node count is really that important. More important is the decentralization of blockproducers. Bitcoin has a few mining pools who control the system.
I'd like to compare Steem posts to the number of Bitcoin transactions that contain non-financial information, but I don't know whether that is tracked.
I'm not sure how relevant comparison it would be. It's better to focus on the most important metric which is the total transactions. Steem has been winning Bitcoin for a while now and we really should emphasize that point to everybody.