The difference between a live engineer and a mix engineer are nothing for the most part except that the live engineer must be on the ball, his ears must be as accurate as possible while ringing out a room, but you can use tools like SMAART to help out and AID you...Don't RELY on them, they're not always correct, your ears are your best tool, don't forget that!
Also with live sound, you're setting up and striking the PA. I've done some shows and have heard from MANY people how most engineers they work with for shows are "assholes" and don't do their job right. It's the truth. a lot of live guys who work in bars and whatnot tend to be doing it for the fame rather than for the act, so they are busy flirting with women and AWAY
from the console! I can understand being away from the console in some
situations. For example, I was out with someone setting up and doing a show for a party and everything was rung out and good to go, so we were able to sit back and relax and enjoy the show, this isn't always the case though.
With live, being a gear head is very essential, especially when it comes to consoles, PA speakers, amps, etc. You HAVE to know your gear well. Generally speaking, all consoles work in the same way, you've got your inputs and outputs, sends and returns, but each board works different from another in certain ways. Read manuals, learn about things like:
In live wattage is literally your lifeline, always bring a multi-meter to check and make sure that your grounds are safe and there are no serious power issues that could kill you or someone else. The ground/lift switch is NOT always your friend either, if you flip that, YOU can become the ground and get fried.
Live world involves very good interpersonal skills and very good ears.
Google SFT to start on your ears, download it and start small, learn 5 frequencies at a time and go up from there.
Live world is NOT an easy one by any means, it requires 16 hours a day a lot of times. Especially for large events.
Hope this helps!
edit: I just realized I read this COMPLETELY wrong XD. I'm still leaving that up there, but now that I've re-read, I wouldn't say live boards
are more "hefty" unless of course you mean price, then yeah, they are pretty hefty lol. LOTS of different boards are used, it changes everywhere
you go, every place has a different board, but the ones you'll want to stick to are:
Midas (check out the verona series)
A&H (even though I don't favor them lol, GL2400)
Presonus (studiolive series is pretty awesome, but takes some doing to get used to)
Soundcraft (really has a lot of options, go to their site and really look around)
Yamaha (PM5D is a beast even though I've never used one, I know all about the crazy stuff they can do)
Do some research of those manufacturers and see if you can find what you like.