My own personal opinion is that Navionics is almost useless in timbered areas. Considering Fork is full of timber you might not like it. I like the LakeMaster but the problem is its so detailed that it can take your GPS longer to update the extra detail when running. I like the fact you set the actual lake levels on the LakeMaster that reflect the actual water lines.
I highly recommend you get the GPS Lake Maps chip and a copy of Lance Vick's Boat Lanes chip to use with either of the above you go with. The GPS Lake Maps creek channels etc are dead on and Lance's chip is worth its a thousand times more in time it saves you running and damage saved to your boat.