Ecobak plus pellets here (warner marine 2nd gen) since they came out. They're touted as a multiple carbon source.(I would suspect a vsv kind of combo, don't quote me though) They work a lot better than the first gen in which I'll admit I had cyano and bacterial mats, but I also didn't have a recirculating reactor. Which in hindsight I think is vital.
I also have mine plumped into my skimmer both for input and output. Meaning reactor input from skimmer output, and reactor output to skimmer input. Thus creating another recirculating system in addition to the reactor. I've successfully kept a high degree of more bacteria in the reactor than I've ever seen.
I have found a 1ml amp of biodigest will establish a reactor in 24 hours, for a 75 gallon tank. The bacteria addition definitely seems more optimal than bacteria from the air, it also greatly helps directly after cleaning the reactor.
Don't think I would ever setup another tank without them. It makes phosphate and nitrate management kinda comical that it was ever a problem in the first place when keeping aquariums. In my opinion it's a step up from vinegar/vodka/sugar dosing in keeping the bacterial colonies mostly out of the main tank.