Hello Paul,
This is a touchy subject and hard not to be subject-ive. I will try to be objective. The big issue here is whether you care about resale or capability or initial price. Your personal feelings toward a certain look. Some folks are looking to match Grand Daddy's truck. So plain and simple: the 3100 is more popular, more valuable, better resale, more aftermarket parts, more available upgrades, less heavy duty tools needed, cheaper parts. It's more popular because it's a short bed lighter duty truck. Larger crowd of buyers. More suitable for restorers/preservers/fixers/cruisers/hot rodders/modders.... who want the best investment return. Those who feel a short bed 1/2 Ton is nicer looking. If you look around, you don't see too many TV shows, cars shows, magazine articles.. on long beds. 3/4 T does not come in short bed. I relate it to a 4 door 56 Chevy vs a 2 door 56 Chevy. 67 Mustang Coupe vs 67 Mustang Fastback. As the saying goes "is that a Hemi?"
3/4 T and up will certainly gain in value. Have many admirers and are very handy if you are hauling frequently. They are built stronger. If strong is what you are after. It is not necessary to pay for a short bed if you like long bed, want to keep it a long time and/or have a use for it's extra capacity.
If you have seen that 3100's sell for more than 3600's, in general, even though you "get more" with a 3600, it supports what I'm saying. It is true in most regions that 1/2T sells for more....and are WAY LESS AVAILABLE.
In the next era up, 55.2-59, where 1/2 T comes in long and short, the short bed values, popularity and unavailability is quite evident. They are even 2" shorter than AD. AD= 116". TF= 114".
Then in 58 came the fleetside. So a 1/2 T short bed fleetside is the "Coupe de Grass" of that era. Add big window, V8, 4x4..... for the Holy Grail.
The same "value quotient" runs on up the years to at least 72.
It's about preference and goals (subjective). I have given you the objective facts.
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