Based on this poll, after corrections were made, and factoring in the response rate for each trans type (4 total), and a total of 28 transmissions analyzed (some had more than one):
All but one 4T60E made it over 100k before first failure (12 over 100k, 1 between 75-100)
All 4T60E(HD) made it over 100k before first failure (8 total)
Both 4T65E transmissions listed failed under 75K
Of the 5 4T65E(HD) transmissions, 3 failed under 75k, and the other 2 failed before 100k.
According to the trans shop that rebuilt the Zilla'* 4T60E(HD), they typically see a 3:1 failure rate comparing the 65 to the 60 (4T65E is 3 times as likely to fail than the 60). Most 65E failures they see are under 75k (which is why I used that benchmark in the poll).
450,000 92-96 Bonnevilles were produced with the 4T60E or 4T60E(HD)
Roughly the same number of 4T65E or 4T65E(HD) were produced from 97-2005 (even though this is a 9-year period of production, the numbers are offset by lower production each year).
Adjusting the numbers to make even samples of each major type, the following conclusion can be made (based on the data we collected):
A 4T65E or 4T65E(HD) is twice as likely to fail under 100k miles than a 4T60E or 4T60E(HD).
While trying to rationalize this, try to remember that even though the Series 2 develops more power, the Series 1 develops it in a more dangerous 'range'. And the 1996 Series 2 L67 mated to the 4T60 trans doesn't see the same failure rates as the newer cars with the 65.
After watching the trans failures over a period of 3 years on this forum, this is about what jr's3800 and I expected to find from this simple poll. Consider this a small sample size, but over 3 years, the trend is there as well.