The current meta in the most recent patch as I write this HUGELY favors early aggresion teams. The average game time has dropped to 34 minutes at the top levels which is not quite long enough for scaling comps to come online.
Look at average win times for a team, and average first kill/first dragon rates, and if it's an early game team that only wins in short games vs a late game team that wins mostly in long games. Right now the early game teams have a HUGE advantage and the books haven't quite adjusted for it fully, probably because the bettors haven't either.
The last patch favors early game characters so much more heavily than it did last patch that it's not fair. Look for teams who's players do well with early aggresion characters, profit.