Like the others stated, it is much more lighter, faster recovery, has target and tone ID, and in my opinion, it will be much better coin shooter with the Digger coil on it, especially in sites where there is a lot of small iron.
I have hunted salt water beaches ( wet sand ) with the 3kHz 9 inch concentric ( remember, some of the coils are NOT WATERPROOF), and it did very well. I prefer to use waterproof coils when wet sanding and the Minelab 3kHz 9 inch concentric gives you the piece of mind of it being waterproof, as well as being able to run stable in the wet, salt sand due to it's frequency.
Since you will only be salt water beach hunting on occasion, the Safari would be marginally better in the wet sand. Venture into the dry sand with an 18kHz coil and you will beat the Safari hands down in the gold jewelry department. I have an E-Trac and use that on the salt water beaches on occasion so I do have experience with both the 705 and FBS units.
The only way I would pick the Safari over the 705 is if you would be hunting the wet sand at salt water beaches a lot (75% or more of your hunting time), or if you had bad soil conditions where an FBS unit would run smoother.
I will put a plug in for the Digger coil....it's an awesome coil. Just remember it is only water resistant, do don't dunk it !