As a standard Straight Router Bit is not designed to plunge, which would be the better tool for profile routing in MDF ???
Pros & cons between Slot Drills & End Mills - which would be better for a direct plunge then feed, cutting 6mm MDF ??
Max Speed I can do is 27K RPM and 250mm/Min Feed rate.

Use a 1/4" upcut spiral, preferably at 12K-15K rpm (maybe even slower) and 250mm/min. If at all possible, try to ramp into the cut rather than plunging straight down. Plunging will drastically shorten tool life, and cause quite a lot of burning.

At work we use mainly center cutting end mills, generally 4 flute carbide, mainly for stainless or 4140 alloy.

Best of both worlds, but as Gerry mentioned they last longer if you ramp them into the job.

Craig

Keep in mind that end mills are designed to cut metal. Spiral router bits are designed to cut wood and wood products. The cutting edge geomtry is different. You'll get better results with the right tools.