No trading advice here. Take your own risks. This relationship does not always work.
To me right now both BCH and BTG appear to be the best buys. There are more people who will bet on BTC 'futures selling' now that the prices are already sky high. If this inverse relationship lasts, then BTG and BCH should theoretically benefit from it. Once again, these are my personal views.
BTC, ETH and LTC are all priced higher, and this is due to the lay man who knows probably nothing apart from 'BTC is going to get higher because of the futures listing at CBOE, so will ETH and LTC' mentality perhaps.
Also, with regards to BCH, when BTC starts to fall, BCH should benefit. Also BTG in my view. BCH will be credited to users accounts holding BTC at the time of the fork in July/August 2017 at Coinbase/GDAX. Trading is expected to begin at the same time. This should have an effect on the prices too.
Should be all over by 11:00 p.m. GMT, hopefully sooner. Target is 50% fib line.
MACD is the key here....
BCH will hence achieve 0.5 BTC value. Anything above it will be a bonus. That will be the time to switch from BCH to BTC.
Just an idea. Just like my friend @qdoc says, do your own due diligence.