I've seen something like this happen before. If some or all your players are enjoying some of the game, but find dealing with the other players frustrating enough that they're starting to get reluctant to attend sessions, there's an important question for which you need to find the answer...
Why are arguing?
Not "what are they arguing about," as you already know the answer to that. Rather, you need to work out why your two groups of players are regularly forming contrary positions.
As some of the other answers have pointed out, players arguing about what to do next is normal. However, if your players are arguing past each other or always ending up forming the same sides when there's an argument, or if both sides seem confused as to why the other side doesn't agree with them despite claiming to have listened, it is likely that your group has mismatched expectations about the game.
Something similar happened in one of my campaigns: There were two groups of players who would have long, frustrating arguments in which they would disagree as to what to do next. Each side would put forth their arguments, listen to what the other side had to say, weigh up the pros and cons of each proposed course of action, and then want to do completely different things.
Eventually, I discovered the actual cause of the argument: One group assumed the campaign would consist of modular adventures in which few-to-no decisions would have long-term consequences that might affect subsequent adventures, while the other group assumed the entire campaign was one big adventure in which every tiny decision could have unforeseen long-term consequences that might not reveal themselves until later in the campaign. Thus, the former group tended to think in terms of short-term benefits and to underestimate the likelihood of bad decisions coming back to haunt them, while the latter group was more prone to long-term planning and highly risk-averse.
It was a tricky problem to identify, as people don't tend to mention the unspoken assumptions they're basing their decisions on. After all, the nature of unspoken assumptions is that you don't think to question them unless something makes it obvious they don't always apply - and getting into an argument about an apparently-unrelated topic doesn't.
Getting back to your situation, I imagine your two groups of players are listening to each other in arguments (even if one or both groups claim otherwise; if they weren't, you'd have a very different problem), so I suspect that they have different assumptions about how the game works. I can't be sure exactly what the point of difference is - you know your players better than me, after all - but here's a list of possibilities that spring to mind:
- How likely it is for players to die when they head into "dangerous" situations. Many games and adventures use "it's dangerous" or "beware the monsters of the forest" or "none who venture into the depths have ever returned" as code for "adventure lies that-a-way." Thus, it's possible that one group of players is assuming "it's dangerous" means "loot and glory awaits" while the other group assumes it means "our characters have an unacceptably low chance of survival."
- Whether, when the GM dangles an obvious plot hook in front of the party's collective nose, the party is expected to bite. Many groups have a gentlemens' agreement that if the GM gives them a thread to follow, that they should follow it, because the GM hasn't prepared alternatives. It sounds like you're perfectly happy for your players to ignore potential adventure leads, but your "courageous" players might not be aware of this.
- How adventurers are expected to act. You may have one group who assumes adventurers are expected to be brave, heroic types who gladly brave danger for the sake of what is right, while the other group assumes adventurers are magnificent bastards who gleefully seek their own advantage by hook or by crook. (I like to call this the "paladin versus thief" problem, as many players expectations about how main characters act are often set by the stories they've read - and stories where paladins are the main characters and stories where thieves are the main characters tend to operate on very different moral and narrative logic.)
- How much the group should care about character death. At some tables, when a player character dies, the party holds a funeral, bemoans their passing, and goes on a world tour to inform everyone the deceased PC knew of their unfortunate passing. At other tables, the party checks if there's a high-level cleric available and the player rolls up a new character. Which is to say, your players might have different expectations about how lightly character death is treated at your table.
- How protected the group is from questionable moral decisions. In some campaigns, if the players decide to prioritize their own safety over that of villagers who've fallen in a hole, the GM will take pains to mention that the villagers are mostly uninjured and get out on their own. In others, the GM will take pains to point out how the villagers perished in agony, and could have been saved if only the PCs had promptly come to their rescue. In still others, the GM will just move on, and neither they nor the party will think much about the consequences of the decision unless it turns into an argument about alignment. In other words, different campaigns follow and encourage different moral logic, and players may expect different standards.
What to do...
Assuming you're able to identify a difference in expectations, the first step should be to tell your players what that difference is, and what they should expect in your campaign. Telling them what it is will give them a tool they can use to resolve arguments when they come up in play, and telling them what they should expect in your campaign will give them they tool they need to realise when their own arguments are flawed - both of which they presumably lacked, or the arguments wouldn't have been frustrating in the first place.
Personally, I recommend against trying to accommodate both groups by adopting an expectation that's a compromise between their expectations. Doing so will be stressful for you, and almost certainly result in both groups getting frustrated because neither of them will have a clear idea of what the right expectations are. (In other words: Don't make the same mistake I did... But that's a story for another time.) Instead, just pick one group of players, and say their expectation is the right one. This may seem unfair, but at least some of your players will be happy - and it's likely that the other group, once they actually know what their expectation should be for your campaign, will be fine with adjusting their expectations - especially if it means they can enjoy a smoother, less argumentative gameplay experience.