I only invest in Ark and just a little bit on LISK so it does not count as investment. I think LISK roadmap is very good and the team is great, but I prefer Ark because I joined them in the ICO phase and I support it until today. Ark has a smaller market than Lisk, so he still has plenty of room to grow and the Ark team is very active on Slack.
I have small amounts of ark and lisk. I think both are nice to have in my portfolio because I see the coins as a long distance investment. I don't panic, I hold and at the end they both will be valuable.