The big difference is almost everything about the two cases. Beginning with early reporting when WH went missing being the first step to locating her quickly.
But, since the car evidence is a big part of both cases, and LE came up with prints and DNA evidence leading to JH in WH's case very quickly, they already had concrete evidence showing the crime involved her vehicle.
Because they did find WH's body, you're right that the two cases can't be compared exactly.
Because of the DNA evidence in WH's car, LE knew who the perp was.
So, the million dollar question is, does LE have DNA evidence from EA's car? And, since they haven't discovered Christina yet, wouldn't DNA evidence be enough to charge EA with something if combined with video evidence too?
If EA's car has gps, aren't they able to trace his route, or by using his phone pings?
If LE had specific areas, TES would come back to perform thorough searches in those areas.
It helps me to look at cases that were solved efficiently and compare the differences with a case that seems stuck.
Because, it seems, nothing is leading to something else. For instance, professional searches.