Depending on your experience, there can be a huge difference in quality. But a good brewer can make extract just as tasty as AG. There are some small limitations using extract, but otherwise, it's very much the same.
Doing AG is more rewarding IMO, if you are interested in how the whole process works. With extract, the fermentables are created for you, and you have little control over how they taste or ferment.
It does save time and requires less forethought to brew extract. But except for the mashing of the grain, it's pretty much the same after that. I would say that if you are confident that you understand and can successfully perform the mash step, then why not start with a batch or two of extract to get your feet wet. While that's fermenting, start building a mash tun.
There are more threads dedicated to the differences, as well as a few books and even a very good website with information on both methods. (plus there is partial mashing, which is a hybrid method).