How do they get a big advantage? They still have to play and win the game, which is from a big pool of maps and settings.
Say you have 5 vetoes per player and 2 member-only templates on the ladder.
Based on MW's suggestion, a non-member only gets 3 vetoes on the ladder(coz the 2 templates are auto-vetoed). On the other hand, members will get a choice of 5 vetoes which is obviously an advantage in terms of controlling what templates you play on/avoid.
A completely unrelated note: it would be nice if in the games, the date and time of creation was marked somewhere. This way I have some idea of how much I should stress about accepting a game. Since it's not marked the game might have been made an hour ago or three days ago as far as I can tell.
You can always look at the game itself to see the creation time(you have 3 days to join). Initially, I did display the creation time on player profiles. But the page is difficult to read on smaller resolutions, and so the column was removed.