Obviously, I’m going to say that pro mastering is better than home mastering, but I think there are benefits to both.
Let’s start with the latter. You’re in your environment, and you know how it sounds. You’re secure in the knowledge of how your room is and feel that you’ve been involved with the process all the way through. You might be into the kind of the DIY vibe of doing stuff, not going out and having other people touch your stuff, which is fine.
But I think pro mastering is better because you’ll get someone with a lot of experience, a lot of equipment, and a lot of knowledge on the sounds that you want to get. The pro mastering engineer has got a wealth of experience. If you’ve chosen the right one, they will know your genre of music and will have dealt with it a lot. Their room will also be set up only for mastering and will have the acoustics treated. Everything will be exactly right for mastering. You get things sounding to a finished, commercial level that they work on every day with commercial artists. You’ll also get another set of ears coming to your mix, somebody who can feedback to you and boost your confidence.
There are a lot more benefits to pro mastering. But if you just want to get it out there, give it to people with a record label, or just want to get it online, then home mastering is enough.
There are tools that you can use like Ozone and get it to a certain level where it’s loud enough. You might not get the fine details or get it to bounce in the same way that a pro master engineer can. But you will be able to get it loud by limiting it. You will be able to get it in the ballpark, so to speak, of how you get it to sound in your room.
Personally, I like to have things as best as I can. I wouldn’t paint my own house, for example. I can, but I don’t because I make it look a mess. I prefer to use professionals for what they do, rather than trying just to be a sort of general DIY-ist.