RCA are usually 640x480 resolution (same with VGA)
I think you're a little confused. RCA (also known as composite) is roughly 640x480 but a "VGA" connector can carry much higher.
In order of quality:
Coaxial - lowest quality (except for broadcast HDTV). Don't use this to connect any video producing box to your TV, if you've got another option.
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RCA/Composite - slightly better than coax, but still low quality.
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S-Video - significant contrast improvement over composite (due to separated color and brightness channels), but the same resolution. The best option for older devices like pre-HD game consoles.
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Component Video - for interlaced SD content this is not a huge leap over S-video, but it allows for HD resolutions.
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VGA (aka HD-15, aka DE-15) - a computer standard that has had it's capabilities expanded over the years. It can handle resolutions much higher than an HDTV's 1080p, and with a good quality monitor will be very difficult to distinguish from DVI. For HDTVs that have this port it can be a fine way to connnect them, depending on the specific model. There should be no problem sending a 1920x1080 signal over VGA.
I'll skip all the digital standards (DVI, HDMI, DisplayPort) because, wireless aside, they should all have the same image quality.