Trust Mfrs and Marketing to cause confusion.
Digital zoom means you have a picture and you are enlarging part of it..in effect you are going to pixilate the picture, but maybe just 20% digital zoom is OK.
Optical zoom is the real thing, but lenses are a compromise so for a given cost a longer zoom will have poorer quality - Unfortunately no-one gives lpm figures so you have to believe a 2ox lens will probabl;y outperform a 50x lens at max ( and indeed all the way, some may say!). However, if you want to 1)follow sport - or 2) small wildlife, then a longer zoom may help 1) for safety by 2) by not frightening the birds off their perches.
The Zoom feature that "extends zooms" may work like this - at wide setting the sensor pixels are skipped regularly, so you record light from the whole width ( Since HD only needs a 2Mpx image and yr sensor is delivering many times this for any "Stills". As you narrow the zoom, it moves the registered pixels towards the centre - this boosts some definition since lenses usually perform best at their centres. However, the longer the zoom the greater the problems with focus and light-gathering - so noise will increase.... an issue indoors.
Ideally you need to try each camcorder - but I suspect the price you pay will determine the real "Image Quality" - but making a Movie isn't only about technical quality. Yet somehow one suspects the more expensive camcorder will have additional features that could come in handy later-on and when you move to 4K, the better-optics will make it a useful back-up camcorder.
[ Oh BTW the best way to handle "wind noise" is to fit a faux-fur muff - will look odd but who cares? . . . Any electronic "fix" is bound to affect quality and IMHO to be distrusted - better not to have it in the first place. .]
Good luck.