My 'day job' (writer for Computer Music magazine) requires that I use pretty much everything. However, when it's time to record my own music, I fire up Cubase - primarily because I have a lot of outboard gear and it still gets on well with most of the old MIDI stuff. It has some decent included synths and effects, though I tend to use outboard gear more in my music simply as a change from my day-to-day work.
If I were just starting out (and on a Mac as the thread starter is), I'd do my best to see if I was truly going to need more than GarageBand offers - it is surprisingly full-featured and one could make full productions without ever looking elsewhere. Plus, when it was time to move to a more feature-packed DAW, any projects made in GarageBand could be opened in Logic Pro. Logic Pro is ridiculously well-outfitted with any effect and instrument one could need. It can be a bit of a head-scratcher, but it has gotten better in that regard over the past couple of years. Because oft he high-quality of the included effects and instruments, Logic is a great choice if you want to use a lot of virtual synths and processors without buying any 3rd-party plugins.
If money is tight - or if you simply want a pro-quality DAW for next-to-nothing, Ardour is well worth a look. I have been using it on a Linux box (and lately on a Mac) for well over a decade and have watched it grow into a mature and sophisticated DAW that can compete with anything out there, regardless of price - and you can get it for as little as a $1 donation (or free if you want to build it from source). Ardour isn't bursting with synth plugins, so you'll have to source your own.
Ableton Live and Bitwig are excellent choices, particularly if you plan to work with loops (and even if you don't). Abelton Live has become something of a standard these days and comes packed with excellent instruments and effects. The interface is easy to get on with and there are bundle options available depending on what you'd like to do. Max For Live is an awesome way to build your own devices and adds a huge amount of power to an already great DAW.
Bitwig's pricing structure is a bit of a head-scratcher, but it's a great environment and its modular routing provides a lot of power. If you are using (or plan to use) analog synths or modular synths, Bitwig offers built-in CV features to control/interact with that stuff (the CV stuff works best with certain audio interfaces, though).
Studio One is also a good option, as it is extremely easy to use. An excellent interface that takes no time at all to learn, but offering loads of sophisticated features, too. It has a cool built-in modular-style plugin routing system.
Reaper is hard to beat if you're on a budget. You can use the demo version for as long as you like with the only limitation being a nag screen at the start. When you're ready to pay, the hobbyist license is quite a good deal. It has some built in instruments and effects, but you'll want to look to 3rd parties for high-end synth plugins.
Reason is... Reason. I personally love it and have been using it since it was a closed rack with only a few instruments and effects. It gets some unfair criticism for what some perceive as its 'sound' but as a DAW it holds up to anything else out there. Plus now you can use VSTs with it. Not that you'd have to! There are enough awesome synths, samplers and effects to last a lifetime in the thing.
Ah, I forgot Tracktion! Tracktion 6 is now free from https://www.tracktion.com/products/t6-daw. Tracktion is a strange duck,a s it ditches the familiar tropes of most other DAWs for an 'all-on-one-page" approach. That doesn't meant it can't compete with the best of 'em though. It's quite easy to use and comes with a few instruments and loads of effects to get you started. And again, it's absolutely free - no strings attached.
This is an excellent overview, thank you 
