The 6309 was a great watch but it has a few design defects, mainly the screw down crown threads tend to wear off as on mine. The crown will not engage reliably now. The new Turtle is a better watch, slightly longer lug to lug, drilled lugs, better crown, better movement with hacking and manual wind. Here for comparison, side by side:
A good 6309 is worth investing in especially if it has good memories attached but the new Turtle is a better diver and being new, more reliably water proof to it's now 200 meter depth rating than the 6309's 150 meter. I always thought the Turtle, old or new, to be a little on the too large side, thus my actual preference for the SKX00X (SKX007 BLACK OR SKX009 Pepsi).
I am going to have to pass on the PADI version of the new Turtle, mine is the Pepsi with the new silicone rubber strap, Walmart online, it was $239.00, got it a month or so ago. Normally I do not like a watch over 40mm to 42mm but the Turtles, old or new, are just shy of 44mm. However, unlike most, Seiko contours and bevels the cases to fit the human anatomy and offsets the crown and as a result they wear like a smaller watch. The 6309 pictured I purchased summer of 1976 and the SRP77X is of course current production. Another rumor has it that the famous SKX00X may be dropped. I hope not as it is a better (smaller) size, better price and nicer looking, more wearable watch.
James