Thought you guys would be interested in this, a study done by a former student at my school:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4673073/
Found that increased Anki use (quantified by number of unique cards seen) was significantly associated with increased performance on Step 1, even accounting for MCAT, class performance, and more. However, firecracker use (same quantification, # of unique cards) was not significantly associated. While I am betting it would be significant with increased sample size, this does seem to suggest that Anki gives more bang for your buck/card.
Personally, I think the most likely rationale behind the difference is that Anki pretty much forces you to get a card correct before you no longer see it that day, whereas in Firecracker I know I have a bunch of cards I haven't fully memorized yet, but keep seeing every other day because I keep giving them 1s. So, I am thinking that I will continue to use firecracker in second year, but only by doing it "Anki-style" using snooze until I get the card right. However, another potential criticism of Firecracker is that Anki gives you better opportunities for looking at pictures and diagrams, while Firecracker isn't the best for remembering things in visual form because it's all text. Thoughts on this?