My experience so far,
Scion Spark: Good clear speed, relatively cheap gear for doing t5-t9, but dies alot both because of squishy factor, the fact that kitting/avoiding for the bot is not that great and also, there are alot of yellows/bosses with "proximity shield".
Cyclone Marauder: Ok clear speed, very reliable and good survival, but expensive to build for mid-high end maps.
Flicker strike: Very fast clear, relatively cheap to build for mid tier, easy to setup bot but because of the backtracking issues and nature of the flicker strike, you spend alot of time walking back for items/chest. Ofc, that doesnt really matter if you dont open chest and have a very strict pickup rule.
The way i see it, its a trade off and you need to chose your class according to your goals. If you fine doing currency farms on low end maps a spark whould probably bee the best option, if you want high end maps you would go with something more beefy. In the end its all a matter of chosing the right class for your goal and ofc your budget in matters of Ex/gear and the time you want to put in to reading/researching/setup.
Good luck!