TV as monitor

Higher refresh rate helps LCD TVs display fast motion like what is found in sports and action movies. The difference between 60 and 100hz means nothing when using the set as a computer monitor, unless you also want to watch actual content on it.
 
Just curious, why chose a 40" or so TV as your computer monitor?

In that case then get the set with the best PQ. Refresh rate won't matter.

Having said that it would be worth making sure the set has a PC or Game mode which Will have lower input lag (think of it as mouse latency) than standard viewing modes (also less picture settings but they don't matter when using a computer). Most lcd monitors advert their input lag as a part of their specs. TVs typically don't do this though most sets input lag is available via google search.

I looked into this a while back and came to the same conclusion. A TV is optimized for TV and a computer monitor is optimized for that purpose. 
The feedback I got was that a monitor beyond 28" requires you sit further away from it. So having two 24" monitors is the most common set up. 
Your neck will get sore pretty quickly if you are having to look up even the slightest from it's relaxed position. Close friend is a Physio Therapist and sees improper monitor placement in workplaces as a growing concern. This is why office ergonomics is important for employers who are trying for better productivity. 
 
Sit your self in your chair set to the proper height so your posture is correct. 
Look straight ahead and relax. Notice your focused field of vision. This is how tall your monitor can be. If you wear bi focal or progressives you might want to try a set of reading glasses with the correct enhancement for the distance to your monitor. I have a set of 1.75 that I use sometimes if I'm doing a long editing session. 
 
A large TV as  monitor is a great idea for a family that watches movies and gaming from across the room on the couch. It is not appropriate for close in work.