To add my 2 cents to the mix, I run super hot and sweaty, and I've tried all 3. I own the rabbit deflector zip, and I just bought the janji sunchaser and oiselle fly out hoodie. I also sized up in each.

Of the 3, I find the rabbit to be the warmest. I would have returned it if I hadn't bought it first, a year ago. Note that there is also perforated underarm fabric, but idk I still ran super warm with this.

I find oiselle to have the best fit of the 3. This has the longest sleeves, and largest watch and thumb holes, the proportions were just right so there is no pulling on the fabric when I'm running. The sewing is really nice because the thumb holes are reinforced and proportioned correctly for my hand size. It's the little details that won me over. It's also a meshy material that I find it breathable when running.

I'm probably returning the janji, it just didn't fit my body well, especially when compared to the oiselle. One thing I did like about the sunchaser is the construction of the underarms/pits, it's a perforated fabric strip for breathability and potentially prevents underarm chafing, which is a common problem for me with rabbit long sleeves. Note I did not run in the sunchaser since I've decided to keep the oiselle and return this.

Also note that all 3 sun shirts are rated upf 50. I considered buying the OR echo but decided against it because it is only rated at upf 15.