Judging picture quality is difficult because there are many variables in the determination of what constitutes picture quality.
It has become popular in some circles to emphasise the comparative quality differences between tape formats and cameras in terms of lines of resolution. In some ways this is unfortunate because many readers don't clearly understand the nature of these lines of resolution and this emphasis may tend to obscure other elements in picture quality which may actually be more important to the final perceived picture quality.
First, what we do we mean by lines of resolution? We don't mean the horizontal scanning lines on your TV set! These are fixed and depend on the TV signal system you are using. In Canada, the US, and Japan we use the NTSC system and there are exactly 525 horizontal lines on your screen. Actually some of these lines are used to convey non-visual information that doesn't appear on the screen proper so that effectively you have less than 525 horizontal lines visible on your TV.
The lines of resolution referred to when comparing videotape formats are actually vertical lines. No don't bother looking at your TV set. Unlike the horizontal lines, you won't see any vertical lines. Think of the vertical lines in terms of how many vertical lines could be discerned by a viewer. The more lines the thinner they get and the harder it is to separate them. This is a bit like the lines on a still photography resolution chart. When you read about the lines of resolution you will notice that they are referred to as horizontal lines of resolution. You may find that confusing, but think a bit. What we are actually counting is how many vertical lines we can distinguish along the width of the television. So this is really horizontal resolution. The 525 horizontal lines in the NTSC picture are thus actually vertical resolution or how many lines there are along the height of the television. Still following?
When you are watching a VHS tape on your TV the resolution you see will be dependent on both the TV and the tape itself. Many older TVs are only capable of resolving 300 or so vertical lines. More recent better quality consumer sets can resolve considerably more lines, above 400. Typically VHS and 8 mm tape are rated at a vertical resolution of 240 lines, 3/4 inch SP at 325 lines, S-VHS and Hi8 at approximately 400 lines, Betacam SP and MII at close to 400 lines, and DVC at 500 lines (although some tests point to effective resolutions of around 400 lines). These values would suggest that S-VHS and Hi8 are as good as Betacam SP and MII, and decidedly better than 3/4 inch SP. This is not borne out when viewing images from these sources. Most people would agree that 3/4 inch SP looks better than S-VHS or Hi8 and that Betacam SP and MII look a lot better. So what's happening?
Well resolution is just part of the overall picture. The reason that 3/4 inch SP, Betacam SP and MII look better than the other analog formats is that they handle colour a lot better. If you were looking only at a black and white picture then Betacam SP and S-VHS would look pretty similar. However the colours using the Betacam SP and MII are a lot clearer and sharper. With the less expensive formats colours often bleed and look murky.
One last point about resolution. Resolution figures are often given for cameras and the camera part of camcorders. Less expensive units generally come out at 400 to 500 lines and better units at 600 to 850 lines. Are the higher resolutions worth it? After all if the tape can only record 400 lines, at best, why go to a higher resolution, at higher cost, weight, and light requirement? The answer is that, other things being equal, a 850 line camera will produce a better looking picture on a 400 line tape than a 600 line camcorder. The resolution on tape won't be any higher but the appearance of the image will be better.
It seems to be a general rule that keeping the quality throughout as high as possible results in better pictures. Remember that the final picture quality is made up of a complex set of variables: the lighting of the subject; the nature of the subject; correct exposure; lens quality; chip quality; digital processing in the camera head; tape format; tape quality (i.e., tape make and condition); VTR quality (make, type, condition, adjustments); editing losses; generation losses; duplication quality; final tape format; final tape quality (original quality, numbers of time viewed, storage conditions); viewing VCR quality (type, make, condition); viewing television quality (type, make, condition, adjustments); and ambient conditions while viewing (light levels, dust on television screen).