As with any manufacturer, locks come in grades of quality and cost, just like any other product family. Locks are no different. Service reliability usually follows the relative cost/quality relationship. The 6730 Group 2 lock today is all but forgotten. It was replaced largely by the 6630, the Group 2M version that qualifies for installation on TL rated safes. For RSC rated safes, the Group 2 rating is the baseline requirement for UL listing. Most safe companies migrated to the 6741 locks long ago where the safe rating would allow the change, because it is so much less costly.
Others moved to other brands, predominantly the LaGard 3300. The cost of Dial & Dial Ring kits was a big factor too, whereas the price of S&G Dials have always been considerably higher cost. It's a package deal, and the combined cost for a set, lock-dial-ring, has been the metric for these choices. Long ago, LaGard offered package prices that were considerably cheaper. For a while, almost everyone in the gunsafe business moved to LaGard with a few exceptions.
In the Locksmith world, the LaGard has a legacy of poor reliability. That legacy came from a bad launch of their products in the early 80's, and a series of poor decisions choices about how to support the industry when they had a serious rash of failures. Those problems were resolved long ago, but the legacy lives on. In the gunsafe industry, the lack of technical expertise of the market allowed the LaGard product to thrive and aggressive pricing placed it in a leading role. There were other players that came and went. The Taylor Resources PPI P70 lock, later bought by Ilco-Unican had it's day. They faded after Ilco bought the company. Then, the more recent player, the Lock1One came to play with a 6730 level knock-off that is now known as the BigRed. This is the lock that AMSEC uses today on all of the gunsafe and residential products, as well as many light commercial safes. The BigRed has been a good lock at a low price, but retained the high quality traits of the 6730.
The key differences in these locks are materials and manufacturing methods. The traditional 6730/6630 locks are a collection of machined and stamped brass alloy parts, as is the BigRed. The S&G 6741 and LaGard 3300 locks are largely made of zinc die-cast and aluminum stamping components. The machined brass parts are far more precise, durable and longer lasting. The brass parts cost a lot more to manufacture, and are made for a far more expensive material, hence the cost differences.
As for reliability, our records don't favor one over the other much in this diverse lock spectrum when used in residential applications. The typical residential user opens a safe once or twice per day. In commercial use, the safes can be opened more than 100 times each day. So, the problem becomes longevity, and this is where the locks with brass components bear fruit with much better wear characteristics, resulting in longer service life. A typical mechanical lock will operate 30,000-50,000 cycles if it is serviced regularly. Therein lies the hitch... mechanical locks require periodic service, and in commercial applications they get that service if the owner is prudent and has robust maintenance programs for all of their equipment.
In residential use, 30,000 cycles is a lifetime, so the longevity of the locks becomes far less evident. Most of these low-cost locks installed in the early 90's will not reach their service limits for another 30-40 years. Consequently, the residential user is not inclined to solicit regular service to extend the life.
Service failures on residential safe locks are mostly attributed to poor combo setting techniques in factories focused on mass production, where the care and precision is disregarded. Another huge source of problems is in the selling cycle, wherein the dealers interfere with the process by setting the safes on simple common one-number combos for display purposes, then later return the combo to the factory numbers when they sell the safe. These dealers are not trained in the delicate process, and they are responsible for a huge source of lockouts and service calls.
Combo locks have a "dialing tolerance", where there is a range around the ideal set-point of each number that should allow the lock to open. Our factory setting process requires the installer to test the over/under range to verify the combo is set properly. This quality step is imposed on our import vendors as well. Every lock is dialed 1/2 high and low to assure each number is set in the middle of that tolerance range. I know most other gunsafe manufacturers hardly understand these concepts. These are lessons learned from decades of making safes for commercial service.
Which brings me to the point of the dialog. Electronic locks. Since I designed the first retrofittable digital safe lock in 1989, it has been a standard of ours to assure a lock that lives service-free for at least 1,000,000 cycles. Yes, that's what I said, one million cycles without any regular maintenance. I can't say the same for any of the "other" lock manufacturers. The UL ratings only require 10,000 cycles. I won't share the brand vs longevity data we have collected, but suffice it to say this is largely why so many have low regard for electronic locks. We have all had our challenges with e-locks as the technology evolved. I can say, without reservation, that the ESL10 and ESL20 lock we make today lasts longer and fails less than any other mechanical or electronic lock made. We keep detailed statistics, and we sell almost every lock made, so this is genuine statistic based on real service reliability.
So, digital locks have a legacy of their own, but that has been polluted by the failings of lock companies to test and maintain a continuous improvement program like our own. Newcomers with products designed in China by engineers unfamiliar with our safes and history have brought a cloud of doubt of e-locks. Some of our own big-name US companies have had wide-spread failures with poor designs and poor quality control, adding to the negative light shed on e-locks.
In the grand scheme, the e-lock is a MUCH better choice, if a quality lock is selected. Backup mechanical systems are a band-aid for digital reliability. The e-lock offers the user the privacy of combo change without anyone else knowing the code. They offer absolute manipulation resistance, as code testing is prevented with penalty lockout periods. They live longer by as much as 100 times. They auto-lock when the door is closed, so there is never the accidental unlocked safe because you neglected to spin the dial off the combo. They don't require regular costly professional service, and they are many times faster to open in crisis conditions.
You choose, but do that with your eyes wide open.