You get more accurate readings from the TNC over the Hobbico level tachs. It is easier to get a lock on RPMs with the TNC and from a greater distance. I've seen the original TNC tach a prop from behind the engine (about 6 feet away). I have the newer one, and it always reads fast from 2-4 feet away, as when I'm holding the plane with the other hand. It is far easier to get readings without bothering where the sun is. I've never had to position a model to get readings like you have to do with the Hobbico. I don't know about low light levels with the TNC. I had my test stand under a covered deck before I bought the TNC. I would use a large flashlight then.

Is it worth the extra money? I would have to say that it is once you actually have it and get to use it some. It is different. I happened to have the extra $$$ at the time, and was tired of cleaning the lens and hoping that my readings were right. Bottom line is that it is more reliable and far safer to use. This is a personal opinion.