There are absolutely resources for these kinds of questions—but they aren’t compiled by DMs for their players. They’re vastly too much work for that. They’re compiled by experts, posted online, and picked over by other experts to ensure their accuracy and thoroughness. After an exhaustive iterative process, you have—you might have—something authoritative to say on the subject.
It’s not just numerical calculations, either. Numbers are the easiest part, but in most cases you’re comparing apples to oranges so the numbers don’t tell you all that much.
Because this process is an enormous undertaking, in most cases efforts are focused on particular options—usually particular classes. You can find “fighter handbooks” or a “barbarian handbooks” or what have you. These will usually be fairly-comprehensive discussions of the myriad options available, often with some kind of ranking or rating system to highlight the best options. Often the “top line” conclusions—especially if focused on a particular aim—can be summarized in a reasonably-digestible form—your best options are X, Y, Z—, but that necessarily requires a lot of trust in the one doing the summarizing. And vetting that person, in most cases, requires digging into the underlying evidence and seeing where they are coming from.
To compare and contrast, then, you have to read—and fully understand—the available resources for both, and then draw conclusions about their relative merits. Even when just contrasting “top line” summaries, you are often talking about apples and oranges. Only in a few cases—say, barbarian vs. fighter, or perhaps battle smith vs. hexadin—are those conclusions even remotely straight-forward.
And new players, by definition, lack the context to make the judgments necessary here. If I say a foo can deal 30% more damage than a bar, as long as X, Y, and Z, you have no concept if that means foo is better than bar or not—because you have no way of knowing whether or not it’s reasonable to assume that X, Y, and Z are true. And that’s the relatively easy case of pure numbers, damage. When you get into more utility options, you don’t even have numbers to work with. What is the value of teleportation? Divination? How do you compare that with the ability to take and deal damage? There are—or can be—answers to these questions, but they aren’t necessarily easy answers.
Ultimately, the really important thing about this, is that this information is not easily transferred. Nothing I do is going to reasonably allow you to work with the same expertise I have. Even if I answer a question, it will be much more giving you a fish than teaching you to fish—because “learning to fish” in this case requires familiarity with, basically, all the answers out there. So until you have asked and I have answered every question—or more realistically, you have consumed the same resources I have and performed the same playtests I have—you aren’t going to have the perspective I have. Which is to say, there’s no way that I can make this “easy” for you.
So, quite frankly, most DMs don’t offer this kind of assistance to players. Figuring out what’s best for a player character is that player’s responsibility, and DMs tend to have more than enough on their plates as it is. Even if the DM has plenty of expertise, the perspective that allows them to understand the relative value of options isn’t something they can just give to players. They can offer advice, but it’s all-too-easy to slide into the trap of telling players what to do—and giving players the impression that they are incapable of making decisions for themselves, in the process.
Instead, most DMs just let players figure it out. Perspective is most rapidly gained by trying, after all, and if anything gets really out of whack, the DM can always fix things later (e.g. give the struggling character an overpowered “blessing,” apply some balancing “curse” to an overpowered character, etc.—you should be clear about what you’re doing out of character here, these are just narrative tools for explaining out-of-character decisions about balance in-character).
Finally, this is also why balance in a game system has value—you have less risks when making your own decisions from inadequate information. The ideal is for players to be able to just choose the options that sound cool to them—and they will be. Few games actually achieve that, but by-and-large D&D 5e isn’t too bad about it—and some of the worst-off situations are fairly obvious even to new players (multiclassing into wizard when you’ve got 11 Int is pretty obviously a weak choice, no matter how new to the game you are—yes, I know the game doesn’t even let you do that, it’s more the principle that I’m discussing).
