From a long lasting standpoint the OC-12 will win hands down. Parts are available readily. On the twin shaft design parts are scarce at best. Everyone who I have met who owns a twin design hates them since they are usually broke. Now granted these are people who no little to nothing about the design (like myself). No one will work on them that they can find. If they had an OC-12 they would be up and running. Again just from a few weekends a month warrior aspect. Not someone who is passionate and dedicated to that brand of drives. Its also nothing personal. I just believe the OC-12s are 100% better and are ALOT easier to work on. Plus there are plenty available. OF course its just my opinion. If someone wants to go with the twin designs then go for it. BUT if they are broke then swap it out for a more modern version.
Again, agree on all your points... my point is one of originality and not maintainability. I will also say that the dual-shaft design is not like a model-T either. I know a number of folks that use them for their sole winter transport into risky areas and they do very well. Most of them know their machines from top-to-bottom/inside-out so they trust themselves.
The other day I looked at a "1200C Spryte." Uh-huh... it was a 3700 with a Spryte body on it. Hello! Not even close to original or meeting the criteria of being a 1200C. What, because it has the Spryte tag in it but no corresponding mechanical systems? Wild.
For reliability, no one wants to get stuck in the wilderness, etc... so depends on how a machine will be used.
BUT... It's just annoying to see classic whatever (snow cat, sports car, military vehicle, motorcyle, etc...) stray from original. It decreases the value to a collector but increases the value for day-to-day so it just depends on how a rig is restored. Is it a full-body-off restoration (ie, the beautiful Weatherby work) or is it a 'regular-use' cat? So, if I want reliability of an OC12 then I'll buy a Spryte unless a person is totally addicted to the body style of the Trackmaster (I plead guilty). The cost of buying an OC12 is not cheap by any means. If a person has a friend or can find a super cheap deal then that blows the scale out of the water but normally an OC12 plus the cost of a 4T10 will equate to that of a Spryte with alot less headache of the change. A 'new-old-stock' OC12 will run $8,000. A used one significantly less...maybe $4,000.
I am also certain that the value of a properly restored 'to original' spec is worth more than a 'daily runner'. A friend of mine invested over $100K in a classic car he bought for $8K off eBay. Insane I thought. He sold it for over $200K when everyone was hitting him with 'you dont get out of it what you put in'. Mileage varies...but no matter how odd the market, a buyer can be found with patience.
Anyway, here or there... I agree an OC12 is more reliable, etc.. but I am disappointed to see Trackmasters (or any piece of classic gear) cut up...can't ever go back...not really...not 100% back as original. A person could take it back 'good as original' but not original.
Some folks may care less about original... anything from "Yea, talk to me about original when my rig breaks down and it's -30 and I have no hope of surviving on foot..." Agree. OK, so I wouldn't take a risky cat out...that being a modern cat that has been poorly maintained or an old classic unless it has been very well maintained. It's always wise to have proper emergency process/plans made no matter what..but you get my point.