There’s some pretty significant differences in operation and function between GB and Logic (Express or Pro). The key differences in my opinion are:
-Ease of use in editing regions (toolbox makes editing, creating crossfades, and hyperdraw possible, such as with the pencil tool);
-Automation editing is far greater; with zoom and track height adjust, it is much easier to edit waveforms; GB limits the volume graph track height, which has always bugged me;
-Plug-ins: apart from the level of sophistication with things like reverb, compression (multi-band compression), and others, visually, they’re easier to operate, and more intuitive for those who have used more conventional mixers (you insert the plug ins from a dedicated mixer insert section);
-Advanced routing: beyond just straight in-to-out paths for audio and instrument tracks, you can route using buses and sends;
-The virtual synths bundled with Logic: ES24 sampler, Ultrabeat drum machine, and Sculpture are amazing; Ultrabeat in particular is worth the price of admission, if you’re into Drum ‘n Bass beats-it has a pattern/step sequencer that is very intuitive, and integrates with the core sequencer seamlessly; also it’s very easy to automate single functions of synths, such as with the simple FM synths, where you can tweak Mod wheels, Oscillators, and Envelopes visually, for the “tweaked out” bass sounds heard in many jungle bass lines;
-Automation programming in real-time using professional standards-touch, latch and hard write automation;
-Import and export tools are pro-level; you can dial up customized output options, such as format conversion, burn directly to audio CD, bit-depth and sample rate convert, etc.
-Quantize and other functions for editing MIDI are far advanced from GB
-Display functions (zooming, track height adjust) truly make workflow faster and more efficient; the design is so much better, that in fact, the most recent ProTools seems to appropriate many of the look and feel elements of Logic.
-Far more loops, virtual instrument patches, and effects options.
As I’ve described to my students, GarageBand is Logic, however, its interface and limited functionality make it seem like riding a bike with training wheels. If you know GB, the transition to Logic is a piece of cake. I do recommend using training tools like lynda.com or the Peachpit Apple Pro Training Series for Logic Express/Logic Pro as a means to becoming acquainted with all of the features.
While it can look overwhelming to new users, Logic’s highly customizable interface allows you to pare down the look and feel of the program, and you can “hide” features, trays, windows, etc. until you really need them. Lastly, I really stress trying to learn the hot keys-it really makes the workflow speed up (not to mention, you will look like a pro to your work associates when you master them!)...feel free to PM me if you have any questions (as I mentioned earlier, I teach this app in a community college curriculum).