I've also got the impression that Ethereum could have harder times ahead. It's currently (this week/month) performing well. But the ICO boom is coming to an end, and other coins with similar scripting capabilities are slowly disputing its leadership in the smart contract business. Problems like the Parity bug are damaging its reputation.
These problems are also reflected in the
Global Charts of Coinmarketcap, where Ethereum is also losing market capitalization share. New competitors increasingly gain access to crypto-investors' capital and network effect.
Bitcoin, in contrast, looks robust - it has recovered a good part of the 2017 rally price increase. And there is Lightning waiting around the corner.
So in contrast to you, OP, I don't think that Ethereum will outperform Bitcoin this year. The points you mention are not really relevant anymore, as smart contracts and "other currencies", as already said, are possible on lots of platforms now, and the capacity problem is about to be solved by bigger Segwit blocks and Lightning. Take into account that Bitcoin was designed to be a means of payment and not so much an application platform, so Bitcoin and Ethereum are not direct competitors in all fields. And Ethereum's killer app still is to be found ...
Conclusion: I think already now it's a good time for the switch. However, I would not rule out a bearish leg with new lows, but this would affect both coins, and in my opinion Ethereum would be affected more strongly.