I've worked at Sandia Labs as a software developer my entire career, so I can't compare to FAANG or SV in general. Obviously I like it, or I wouldn't have been here for 20 years.

Their job classification system is such that you will want a Masters degree. I joined with a BS in CS, and until I got my MS, I was categorized as a technician and was paid the same as say someone who soldered and assembled electronics - just over half of what someone with masters in CS would get with simular rankings. I've heard it has improved since then, but there is still stong bias towards those with a masters. For many engineering jobs this makes sense, but it is out-of-touch for computer programmers and security researchers.

Apart from that while the pay is less than SV, all the labs except LLNL are in parts of the country with much lower cost of living as well, so the pay is pretty darn good for the area IMO. Benifits are good, but not exceptional. Work-life balance is great. I've hand a handfull of month-or-two long crunches in a 20 year career where I had to work 60 hours a week. The rest of the time I work my normal 40 hour schedule and go home. They have standard, 9-80, and 4-10 schedules as options (which nearly all managers will approve). After years of having every other Friday off it would be hard for me to go back to a normal schedule.

The actual work varies wildly with the project you are on. Nuclear Weapons work is extremely slow and process heavy as you might imagine, others are more nimble. Projects I've been on have varied from solo development writing software for the engineering next office over, to small agile teams on quarterly releases, to 5-year waterfall development cycles which a huge team. I've done everything from microcontroller software for sensor systems, realtime streaming data processing, desktop data analysis software, web tools for managing data stores, to pure algorithm research. And that is just a small sample of projects going not even touching supercomputer simulation or security work, that I have no experience with. I feel like I have had a great balance of interesting and stimulating technical work and necessary grunt work. Needless to say it is hard give a single "this is what working at the labs is like", and individual experiences will vary.

There are some differences from industry that are independent of the project, particularly around security. It is not uncommon for software development to be done at the unclassified Official Use Only level, but (production and test) data to be at the classified level, which is done on separate networks (or stand-alone computers). Moving between the two environments can be a time sink. Getting approval to use third-party libraries on classified systems can be a very slow process (weeks at a minimum) depending on the network. If the generic security plans won't work for your project developing a custom one can take the better part of a year. There are many security processes for which I completely respect the purpose, but am flabbergasted at the inefficiency of the execution. Contributing patches back to open-source projects is painful enough that it is rarely done. There is some third-party software that is prohibited (like JetBrains due to connections with Russia), and cloud based tools (on the public internet) are obviously not allowed. You need to be constantly mindful of what you type/say to maintain OPSEC and avoid leaking classified onto OUO systems, or leaking OUO to friends and family.

They are allowing WFH now, but most managers for most jobs will want you start on-site to help acclimate to the security culture, and to live in town to be able to come on-site to work in the classified environments when needed. You will need to apply for a security clearance once hired, and some projects are better than others at finding meaningful work for you to do while waiting for the security clearance to be granted.

As far as ethics go, on one hand you won't be asked to write dark-pattern advertising-driven manipulative spyware. On the other, most work will be related to defense applications directly or indirectly. There are some projects related strictly to energy generation and power-grid security and the like, but they are the exception. The best way to advance your career in the Labs is to move around between departments every several years, so you will be limited in your options to do that if you have reservations about defense work.