Do you prefer a small (3 or 4) or large (5 or 6) party? Why?
Ultimately in a large party it feels like your character gets so much less time in the spotlight. The larger the party the less time you are a protagonist and the more time you are a spectator.
In large parties, characters often feel redundant. In small parties, it can often feel like you have a niche that your character excels in. In small parties all characters feel integral to the party's success.
For larger parties, it is harder to make sure that everyone's voice at the table matters. Often players fade into the background or even completely disengage without the DM even noticing.
Large parties suffer from slow combat as there are more players and more monsters to compensate. There is also more to keep track of slowing down the game further. DMs often have to rush players to keep any sense of reasonable pacing.