There are differences between DME and LME. Taste, color, and something what I call a malt extract specific "character," a bit of a certain undertone, that you won't get from 100% AG.
Because of stale canned LME warnings all over the brew boards I've been avoiding cans of LME. Who knows how old they are and how they were stored? Instead I've been using Briess or Muntons DME exclusively with steeping grains. The results were very good. Maybe not as good as AG in skilled hands can be, but very appetizing. Like 90-95% of the way there.
When we moved our new local HBS pours fresh LME from 33 or 50 gallon vats. It looks and tastes very fresh and they sell a lot of it, so it remains fresh. I made a couple batches with their LME.
I think there's a particular flavor note ("character") that comes with LME. A sweetish twang. The DME also has some twang, but is a drier and perhaps somewhat lighter one.
The twang I taste is similar to, but much less pronounced than, the difference between powdered instant coffee (compare DME) and liquid coffee concentrates (compare LME). The malt flavor of both extracts is different from what you get with AG brewing (compare freshly ground coffee beans), which if done right can give you the cleanest, freshest tasting wort, with none of that underlying extract twang "character."
Now for the beginning brewer in general I would encourage to brew with extracts first. Once you get a handle on the whole process, and know what to expect from a home brew, and feel you want to make your brew life more complicated, you can decide to step up to AG. The start of a new adventure. I love mashing grains, it is almost more rewarding than the boil itself.
Just to put a perspective on this, I was using extract up to now and have just made the switch to AG brewing.