I entered a tournament with 46 players at the start time, & by the time play started there were 60 plus players who miss the first few hands. I never know when i enter if i’m playing against 30 or 60. my odds are diminished by this.
At the moment Replay has a short time for late registration. It is 5 or 10 mins or when the reserved seats (10% of the numbers of players start in regular time) are filled up. A lot of players register in the last mins of regular register time and in the time for late registration.
Now the time is too short to talk about advantages or disadvantages.
For players who registered in regular register time the benefit is that the prize pool goes up, how more players how higher the prize pool and more to win. Late registration is a part of multi table tournaments.
When the late registration time is longer (30 -60 mins) it will be a personal choice. If you want start from the beginning and have smaller blinds (easier to call the small blinds) or you start when the first players are out or have a small stack already, but than you must play against players with high stacks. And start with higher blinds. If you started in regular time it is possible you have less chips than a player who starts by late registration, you lost your chips to players who already play, you need to win hands to win a prize in a tourney, you need win from players who already won hands and from players who start by late registration.
There are many opinions about late registration (and rebuy options which not available yet on ReplayPoker) But it is a part of the game.