If it wasn't for casting, I could not have afforded to shoot so much for 45 years. I have molds from Lyman, Lachmiller, Lee, RCBS, and one or two "something".
IMHO, it does not matter so much WHO made the mold as it does how YOU take care of it.
Be sure the bullet profile is what you want before you lay out the $$$.
Aluminum or cast iron ("Meehanite" was the best of the cast iron, seasoned and tempered before manufacture) - either one will work well, but they will not work the same. Learn the characteristics of the mold you are using, and it will be a pleasure for you. Proper preparation is essential, scrupulously clean the mold before even heating it, lube it with colloidal graphite, and coat the insides of the cavities with the same.
Be aware of the venting of the air from the cavities when casting. (It's gotta get out so there is room in there for the lead, you know). Having proper temperatures of mold and lead is key to getting good bullets, and as sp1969 said,
"Aluminum warms up quick and cools off quick, too. You'll be casting good bullets quicker with an aluminum mold, so aluminum is probably a real good mold to start with".
. . . . and I would second that sentiment.
When you are done casting, let the mold
cool completely, and then sink it in motor oil until you are next ready to use it. To use it then, just clean the oil off, reapply colloidal graphite, and CAST. You will prevent rust in the cavities, which is a real bummer for a good casting process, and even if you ever DO get the rust out, it will cast a "non-standard" bullet. Some folks argue that to leave the last cast bullet uncut in the mold will prevent rusting, but there are as many on the other side of that argument, saying that is a ready trap for moisture, and you won't see it until it is too late. I use the oil method, after "losing" one good Lyman (357 DEWC) mold to rust.
Good lead can be had still - scrounging is not all that hard. Cleaning out the backstop at the range is easy, the stuff is concentrated, and relatively pure for your purposes.
Flash