IMO, the value of a course depends in large part on the instructor. Properly conducted, and especially if tailored to challenge the individual student, I think any of the courses, including Buoyancy and Navigation can be worthwhile.
PADI course overviews for those you asked about follow. The learning objectives from each course would be a much longer list.
Multi-level Diver
1. the planning, organization, procedures, techniques, problems and hazards of multilevel diving.
2. definition and advantages of multilevel diving.
3. methods of calculating multilevel dives (The Wheel and/or dive computers).
4. review of decompression sickness theory.
5. review of emergency decompression procedures.
6. review of PADI’s S.A.F.E. campaign.
7. procedures for flying after diving.
8. guidelines, rules and procedures for multilevel diving with the Wheel and/or diving computers.
9. care and maintenance of dive computers.
Deep Diver
1. planning, organization, procedures, techniques, problems and hazards of deep diving
2. risk factors and decompression-tables review
3. safety stops and emergency decompression procedures
4. special equipment, descent lines and buoyancy-control considerations
5. procedures for flying after diving and high-altitude diving
6. orientation to recompression chambers
Navigation
1. the planning, organization, procedures, techniques, problems and hazards of underwater navigation.
2. methods of estimating distances underwater.
3. natural navigation techniques.
4. using underwater patterns.
5. dive site relocation techniques.
6. compass navigation techniques.
Wreck
1. the planning, organization, procedures, techniques, problems and hazards of wreck diving
2. the preparation and use of lights, air supplies, special equipment, penetration lines and reels
3. limited-visibility diving techniques and emergency procedures
Cavern
1. the planning, organization procedures, techniques, problems, and hazards of cavern diving
2. special equipment considerations including, but not limited to: lighting, guidelines, reel handling and redundant breathing systems
3. proper body position and buoyancy control, air-consumption management and emergency procedures
4. information that describes the specific hazards of cavern diving should include, but not be limited to: silting, line entanglement and breakage, disorientation from permanent lines and emergency situations unique to cavern diving
Drift:
1. the planning, organization, procedures, techniques, problems and hazards of drift diving.
2. special equipment -- floats, lines, reels.
3. proper procedures for buoyancy-control, navigation and communication.
4. site selection and overview of aquatic currents – causes and effects.
5. techniques for staying close to a buddy or together as a group.
Peak Performance Buoyancy:
1. Peak Performance Buoyancy fundamentals:
• Buoyancy check.
• Fine-tuning buoyancy underwater.
• Weight position and distribution.
• Streamlining.
• Visualization.
2. Use of PADI’s “Basic Weighting Guidelines.”
3. An opportunity to polish buoyancy control beyond the Open Water Diver level:
• Positioning and distributing weight for comfort and desired body position (trim in the water).
• Visualization techniques prior to dives.
• Buoyancy checks.
• Establishing neutral buoyancy during all segments of a dive.
• Fine-tuning neutral buoyancy underwater.
• Hovering.
