Well I could be off the mark here, but pretty sure this correct....
They're essentially 2 different games, obvisouly a lot in common but thy're 2 seperate things. I don't believe you get FE with LH. If you pre-order LH you would be able to play in the beta but you wouldn't be able to play FE.
If you buy FE now it will cost you about $30. Then you can upgrade to LH later if you want probably for about $20.
If you buy LH now you'd only get access to the LH beta (no FE) and it would cost you about $40 (I think).
I'd recommend the first option, go get FE and get stuck into it, it's a cool game.