I like my .32 Crockett squirrel rifle quite well overall. However, if I had to do it over again, and from the choices you listed, I would most likely choose the Investarms .36 caliber. Reasons are:
1. I find the small .32 caliber RB to be a bit difficult to handle, especially with cold fingers and/or in poor light conditions. If the ball is not swaged and has a sprue then it makes loading even more difficult.
2. IMO, the Traditions is not the most high quality made rifle overall. I do not like the wood used to make the stock, I do not like the finish, I do not like the shoddy factory ramrod, and to be quite truthful, I do not like the drop in the stock.
3. Through much testing, I have found that the Crockett is not the easiest ML to master, in terms of accuracy. I find it very picky as to the correct hold on the shot. It does not like a firm hold and if I choke down on it, its a miss. However, with a proper, good rest, the Crockett can be shot very accurately. IMO, the Crockett is truly one of those "Aim small, miss small" rifles. More so than any other rifle I have ever shot in my entire life.
4. I question the need for the somewhat longer barrel. From my real world hunting time with my Crockett, I find that between the drop in the stock and the somewhat longer barrel, I'm always banging and clanging it against something out in the woods. Never has such an issue with a Hawken, New Englander, or Renegade style ML.
5. The smaller bore can be a pain especially when trying to center the shooting patch.
The Pro's of the Crockett:
1. It's light to carry through the woods.
2. Its narrower diameter makes it nice for in the woods as well. My hands fit nicely around it while hunting/walking in the mountains and/or while getting a rest against a small diameter tree when squirrel hunting.
3. Its very economical to shoot.
4. The accuracy of the Crockett can be quite nice.
5. The report when firing is, IMO, fairly quiet. This has enabled me to kill several squirrels out of the same tree within a few minutes of each other.
6. The Crockett is a nice looking little ML IF one likes brass furniture.
7. Its a very fun little ML to shoot and hunt with.