They use C0 carbide which is the softest. I just had a 1/4 in straight bit break on me! I have a set which I bought some time ago. If I wear one out then I go and buy a good bit to replace it. I usually buy ceap, and if I use a bit enough to wear it out, I figure I need a good one.
Read this and-
Had a "Ryobi" branded 1/4" straight carbide bit come apart on me 2 days ago. Piece stuck in a wall. I know what I was doing... Routing aluminum with too high a bit speed for the material. I could have used one of two die grinders with carbide bits... but I wanted the effect.
I'm sorry, but I try not to bash. I had another carpenter that I worked with that with a good sense of humor, used HF tools every day. His philosophy was- it's cheap. If it breaks, buy another. It worked out for him. My boss and mentor at the time, brand name, get what you pay for/pay for quality.
Other experiences since: Sometimes it's hard to get quality work from inferior tooling. Sometimes you can still get that result, but with a lot more effort.
Yet I still have to get real with finances and I have to compromise sometimes. With that, there's still that "expect what may happen." Adjust and modify. May not last as long. May "have" to make it work.
HF bits and blades? Inexpensive. May not last long. Pay attention to what it's made out of and of the "measurements."
As for routing aluminum... I usually keep a few bits to use just for that, instead of thinking they're going to work just as well on wood afterwards. Bits coming apart? About 10 or so in the last 30 years... but that is using a router "allot" almost every day.