This pretty much applies to all sheet goods.What I have read is that with MDF you should cut as fast as possible
A good 2 flute spiral is actually capable of cutting 3/4 in one pass at about 700ipm at about 16,000 rpm. But you'll be limited by spindle power and machine rigidity on how fast your machine is capable of cutting.
At 100ipm, I'd recommend running the spindle at about 10,000 rpm. I'd actually try to cut in the 175-200ipm range at 10,000-12,000 rpm.
You'll get the best tool life at the highest possible chip loads, which means high feedrates and low rpm's.
3 flute tools are really only used at very high feedrates, as they should be cutting 50% faster than a similar 2 flute for a given rpm.
High quality, long life tooling will run about $90 per bit, and are usually made of a harder grade of carbide. Vortex Tools XP series is one. I use a similar too from Active Tooling.
A compression spiral is what I'd recommend, as an upcut will leave a rough top edge, which will worsen as the tool gets dull A compression spiral will give cleaner edges, even as it dulls.
If you're not doing a lot of parts, 2 flute carbide tipped straight bits are probably your best bang for the buck option, especially if your limited on feedrate. They are much cheaper, and can be sharpened for about $5 each, compared to $15-$25 to sharpen a compression bit.