You want to compare the 'near-bridge' pickup in early '66 and back SF I with the neck pickup location sound in the later SF I basses, right? Well, bear with me. First things first.
Why did Guild come up with the 'near-bridge' location in the first place? Maybe because the 'near-bridge' position is in the same relative place on a 30" scale as the Precision bass pickup is on a 34" inch scale.
That said, the 'near-bridge' position on the earlier SF basses is maybe 1/2" further away from the normal bridge pickup location on most SF II basses (excluding prototypes of SF I 'near-bridge' basses that were factory modded to receive a neck pickup as Guild developed the SF II concept, etc.). The pickup locations are so close that 'sound' of the basses can be adjusted to suit the preference of almost all individual players.
So why did they come up with the neck pickup location? Perhaps Guild realized that their chief competition was not the Fender bass, but the Gibson EB2 bass, which had a neck position pickup. Why did Gibson put their pickup by the neck? Because in the good-old-bad-days, all the amps were crapola and if you wanted a big muddy thump out of a 30" scale bass, you had to have a neck pickup.
So now, how do you compare the 'near-bridge' sound with the later neck pickup sound through modern amps? Beats me! I think they all sound pretty dang good these days!
In conclusion, how good the individual bass sounds to the individual player is more important than pickup location. If a bass 'speaks to you' doesn't have to be determined by pickup location.
Doesn't mean an NS Bisonic reissue sounds as good as the Real Deal, though.
Good luck!