There's too many considerations to list them all. Heat dissipation, beam dispersal, quality of connectors, electronics packaging, DRL compatibility, indexing for proper alignment and a lot more.
On my Hino I lost the doors behind the headlights so the back of the bulbs were open to the elements and road spray cast off of the tires. The medium quality bulbs I had were not bad--good connectors and beam dispersion, but they used cooling fans which allowed water and debris to be sucked into the headlight housing which sprayed schmoo against the back of the lens. They cost about $70.00. When one went bad I bought a $10.00 set that scattered light everywhere but on the road. They were so bad I decided to drive with only one headlight until I could get another medium quality bulb.
Recently I replaced those with Morimoto 2stroke 3.0 bulbs. They are excellent quality that locate the LED chips exactly where the coil of the original H4 halogen bulbs are along with precision reflector cups so there's a very sharp beam pattern. What I like the best is that they're fully sealed into the housing. They have fan cooling, but the fans take in air from INSIDE the housing and then also expel it into the housing. This prevents sucking in outside debris and also it provides a little heat to help melt snow and ice buildup on the lens like halogen bulbs do.
Each application will vary as well as your preferences and priorities. Like I said earlier, I found the videos covering all these topics and more very informative to compare all kinds of features. You can even browse by what fits your vehicle or for a certain size bulb and get a full rundown on the pros and cons of each manufacturer's bulb including an actual demonstration of the bulb inside a headlamp and what the beam pattern is compared to stock.
For what its worth, the Morimoto's are on sale everywhere for just under $200.00, but there's a lot of good quality bulbs out there. Some that are even higher priced have lifetime warranties. You have to do the research for your needs and vehicle then decide based on your circumstances, priorities, and budget what's the best bulb for you.