I think for someone starting out the answer is easy. Since the app itself is run on programming designed by an outside party, functionality should be essentially the same and the community built here at steemit, where you have contact with members, all the way up to the founders and a completely transparent ledger, showing you exactly how stable the economy is,makes it unique. As to block chain, I am sure there are intricacies I fail to understand, but it seems to me, that provided the system is stable and secure, the rest will work itself out, since it is directly in the interest of every member to improve the system, since they directly benefit from it.
As a side note, I think Heat Ledger may have close up shop, so it would probably not be in contention for your future projects.
So...
2.Why do you say/foresee that Heat Ledger will have to "close up shop?"
I must have taken a bad link, landed on a page that said heat had closed and was disbursing tokens starting Aug 22, thanks to all investors. But, now that same link doesn't look the same.
I was suggesting that after looking at what the other platforms currently offer, the social impact of steemit on helping launch might make it easier for a first attempt.
for integrating an app into steemit, i imgine the best would be bitshares.. because its graphene based just like steem is.