The accuracy will be better on the target ID, for a couple of reasons.
1), more likely to only cover one target.
2) The amount of field data is "less" making the processing very efficient. (for example, large coils will false easier in sand, and won't grand-balance as easily, due to the extra data being processed).
3) There's a cost to a large coil, just as there is a cost to a small one: you'll get far less coverage with a 5x8 coil. This may, or may not work in your favor. If you're spending too much time trying to separate targets, it'll cost you in volume of targets recovered. Likewise, you may improve your target separation, but it'll cost you in amount of ground covered. Trashy environments, the 5x8 is better than others, in less target rich environments, the larger coils will find more, simply because they'll cover more ground.
4) Your arm won't wear out nearly as fast... 5x8 is a lightweight! If you were to move to a larger coil (such as the NEL hunter or NEL Thunder), you'll cover LOTS more ground, but the cost to your arm and shoulder is significantly more noticeable. If you're a casual hunter, lighter weight coils may improve your total experience, simply because you can hunt a bit longer, (Which ends up with roughly the same coverage). If you hunt lots, for longer periods, you may find your finds rate goes down with the smaller coil.
Ultimately, it comes down to enjoyment. You can find happiness with either size coil, and both will work. Try it out, and if it doesn't work, as you've no doubt noticed, there's a market for the smaller coils.
Cheers,
Skippy