Got the following from the Tektronix Video measurement glossary (255 pages of good tech info). Tektronix are one of the premier suppliers of video test equipment.
What’s Wrong with NTSC
A. Monochrome and Color Defects
1. Due to Sampling
• Temporal Alias
• Vertical Alias
• Vertical Resolution Loss
(Kell Factor)
2. Due to aperture
• Visible Scanning Lines
• Soft Vertical Edges
3. Due to Interlace
• Twitter
• Line Crawl
• Vertical Resolution Loss
(Interlace Coefficient)
4. Due to Transmission
• Ghosts
• ICPM
• Group Delay
• Impulsive Noise
• Periodic Noise
• Random Noise
• Interference
• Filter Artifacts
5. Due to Changing Equipment
• Non-Linear System Gamma
B. Color defects
1. Visible in Monochrome
• Cross Luminance
• Visible Subcarrier
• Chroma Crawl
• Gamma Problems
• Detail Loss Due to Filters
• Visible Scannig Lines • Ringing Due to Filters
2. Visible in Color
• Cross Color
• Detail Loss Due to Filters
• Ringing Due to Filters
C. Characteristics of the System
• Motion Artifacts, (Not Necessarily Defects)
1. 4:3 Aspect Ratio
2. 330 x 330 Resolution
3. NTSC Colorimetry
4. 15 kHz Sound
Changing the sub-carrier phase on alternate lines (PAL) helped to eliminate a lot of colour defects. The old joke was that PAL = Pay A Lot (of money) as it was more expensive to implement.
The Amiga's video output in PAL or NTSC is not fully compliant with the video specifications. The Non-interlaced mode has no equalising pulses but outputs alternate fields of video as per normal interlaced video.. This can cause some issues with equipment. The interlaced mode was better but there were issues with the timing in the vertical blank period.
RGB PAL or NTSC with the correct cabling and a decent monitor can be very good quality. Composite NTSC/PAL is easy to spot when you know what to look for. Case in point, on my holiday to the USA last year, the in flight entertainment system had a colour bar pattern to adjust the video brightness. From that pattern and the noise artefacts on the text, it was obvious Virgin Atlantic uses PAL composite video!

I design embedded video systems for a living using PAL/NTSC and various digital formats.
Ian