I love biocubes for their all in one setups. I think they are a great starter tank.
I also would say go for the 29g model, just a little more money but opens up being able to get more fish.
While you can piece a tank together for a similar cost, it is a hassle that new salt keepers might not want to deal with. I started with a 29g standard tank myself and as a newbie it wasnt the easiest thing to do. I much preferred my biocube which I got a short time later. I recently sold it and regret it, it was a really nice setup. I had added a t5 fixture in place of the stock lighting and it was a very cool tank. I will def be on the lookout for another one.
Innovative marine also has similar all in ones but they tend to be a bit more money but they really are awesome tanks. And you can add your own lighting as well as a skimmer and reactors. Just depends on what your budget is.