Generally, for large amounts of material removal, and if you’re doing larger parts, the 1/4" end mill is exactly what you want, it allows high cutting speed without deflecting a lot.
I would recommend going with a 90d V-cutter, unless you have a specific reason to go with a 60d (doing finer engraving work will likely give better results with the 60, but for larger work, the 90 is going to rule).
You should highly consider a 1/8" collet, or collet adapter if you plan on doing finer work.
Over-all, Carbide 3d has the best price on most of the common tools (1/4, 1/8) and would recommend you purchase from them, mcmaster-carr sells similar tools, for about %160 of what C3D does. (C3d 1/4 end mills are $25-30 for 3, mcmaster is $20 ea)
Generally, I would recommend sticking with carbide tooling, I have some work coming up I was going to try running HSS tooling with it. (cutting brass, HSS is king!)