Not really, 3 out of 6 society isn't that crippling, the difference isn't going to get past 15 per month, and if it's past 15 it means we have 5+ primitive worlds, so we're probably doing pretty well for ourselves to already own so much space.

Also directly studying the locals too soon makes them resentful. One could argue that is not much of a big deal either too.
Okay, but you've missed the point entirely. You're not competing with a guy who is just doing active observation versus passive observation. What that guy is doing is technologically ascending 5 worlds, starting with the most advanced. Once they're protectorates he's already recouping the lost energy and society research by getting them to add to his fleet strength and influence each month. If it's early enough in the game and he's been unlucky in neighbors, he's popped a migration treaty and lured out at least one population which grants him an entirely different habitability range. Then once those worlds have gotten to be vassals, they add even more to his fleet strength and then he's incorporating them. Once they are incorporated, well, it's much more than 3 society research that he's gotten ahead of you by.
When he set about the path to technologically enlightening the primitives, you gained an 8 society a month research lead over him. Since he's smart he only technologically enlightened atomic and space age civilizations which means your lead lasted 40 months. Afterwards you had a 3 society a month research lead over him and he had a .5 influence research lead over you. The protectorate turned into a vassal and now you have a 3 society a month research lead over him and he has a bigger fleet than you. Now, assuming this all happened in the early game, it took his protectorate lets say 5 years to get to 40% of his tech level and become a vassal. That's an initial research lead of 320 at the end of a 40 month enlightenment, and 180 research lead by the time his protectorate becomes a vassal. Even forgetting his influence gains. How much will those 500 research points worth of green techs help you against his larger fleet?
no. you're comparing Observation Post to a captured primitive planet. you can't do it as every playstyle so this comparison is wrong.
Technological ascension also rewards you with control over a planet. It just takes longer and gives other bonuses that are usually superior to 6 society research throughout. So no, the comparison is solid in the long term.
In the short term, it's comparing 6 society research to .5 influence and a rather pathetic war ally. This is the only part where it's debatable, and then only because of the 11 society research and 5 energy difference between active observation and enlightenment. My rule of thumb is to make the decision based on technology costs as a function of the time it takes to enlighten a society in months multiplied by 22. So before I enlighten an atomic or early space age civilization, I'll need to be on society research techs that cost 880, which will be double the 440 society I've lost in the process of technological ascension. If you're wondering, that's also 11,000 research techs before I even look twice at ascending someone in the bronze age. Those ass backwards guys I leave for the violent militarists or until I'm so large that my tech penalties turn mid to late game techs into 11,000 research.
Then they become vassals and you're comparing 6 society research to a legitimately useful war ally and fleet support. With more fleet support you get a more powerful fleet which provides a significant diplomatic bonus and protects you from the more aggressive or expansive neighbors.
Then they become a planet in your empire and, well, we're not really arguing about whether having a planet is better than having a research station. But this is the only stage where you make more society research following technological enlightenment than you would have from dropping an observation post and forgetting.
There's a very early stage in the game where it's better to keep an observation post around a world, the same part where research labs and mining stations make up a significant part of your in game economy. Get past that point, and the only reason to continue observation is if you're roleplaying the Federation and you feel like saying "Prime Directive" a bunch, or if your energy gain is in the tank, possibly because you're already enlightening some other planet or you have colony ships out.