They compare between PTTGC and TOP that short or mid-term TOP will more bullish than PTTGC. If you hold PTTGC you should switch to TOP, Doesn't mean TOP will go up but if you hold GC there will have more Loss. So let see what happen in the Future.
The reason that GC will underperform is about Spread of Petro Chemical. When Oil go down GC will gain but now Oil is going up so it opposite.