They're both well made, good options, and have their pros and cons.

The main differences:

Tarsier
More aperture adjustability due to the iris design
No closed aperture (fully closed)
Increased possibility for accidental refocus due to iris design
Slower to switch from small aperture to fully open native focus / infinity focus

Hopelite Gen 2
Less aperture settings
Has a closed setting (basically a solid lens cap)
Less possibility for accidental refocus
Faster to switch from small aperture to fully open due to flip cap design

The Tarsier is better if you're routinely in higher light conditions requiring near focus capability as you have maximum aperture adjustment and the Hoplite Gen 2 is better if you need the ability for quickly changing near focus-to-infinity or whatever you native focus is set to.  

So for example, the Hoplite Gen excels at quickly refocusing to near focus by closing the cap such as doing something to a door etc. and then quickly going back to native focus for maximum tube performance by flipping the cap open to allow more light in.

Basically, if you're doing things where seconds count the Hoplite Gen 2 or original Hoplite is a better option IMHO

I forgot to point out in my reply above that the Tarsier Eclipse and Hoplite Gen 2 are both 100% Made in the USA, they both have NSNs, and US Patents.

This is especially important info for those seeking US Made items for their organizations.