Unless you're builing a car that will take hours on a real racetrack, solid rotors will give you the best performance. They conduct more heat away from the brake pads and fluid and are mechanically stronger so they're less likely to warp.
Modern brake pad technology has nearly eliminated green fade, which is the major reason for slots / cross drilling. Unless you are using race-only pads, you probably don't
need it.
If you just want the look, stick with slotted. Cross drilled rotors are more likely to crack. If you really want cross-drilled, stick with the top of the line stuff like Brembo or Wilwood.
