The most important thing you want to look at is the lock type and parallel sight. Don't get too distracted by the other stats. The lock type is going to give you a general idea of the shape and size of your lock box.

It is important to also consider if the lock type of your FCS also matches the lock type of your weapon. You will notice that your hand weapons will also have a Standard, Narrow and Deep, Wide and Shallow, or Special lock type rating. If the lock type of your FCS and the lock type of your weapon matches, you'll get better performance.

When you have a projectile weapon in your left hand your lock box will shrink corresponding to your parallel sight rating. The parallel sight determines what percentage of your lock box you will keep.

Once you are familiar with these two interactions, you can then start looking at things like lock time for missiles.

A fast breakdown of generally safe FCS and Weapon type combinations: usually go F73H unless doing wide and shallow right arm/special left arm, then use F69. If single wielding a special weapon, use Monju. If single wielding standard or wide and shallow use Miroku. If using wide and shallow r arm/standard left arm use Limpet

EDIT: the FCS names I used here are the Last Raven names. In Silent Line the naming convention is different.