Justa - I have the "big dog" of that same amp line - the Fender Cyber Twin, and it truly does have some nice modelled sounds - esp. the bank of Fender vintage amps (Bassman, Tremolux, Champ, Vibrolux). If you're partial to the Fender Tone, like me, it'll suit you very well. Prior to acquiring my Twin, I had a Cyber Champ, and it, too, was a great-sounding little amp. As a comparison to the Vox, I'd have to say that liked the Vox's modeled tones a tad bit better vs. the Fender Cyber Champ's, which I think is in part to its unique tube-hybrid design. The cleans on the Vox seemed to have a bit more "headroom", and its OD amp models a bit more "organic" - i.e. "tubey". The Twin has some unique features to it that allow one to switch drive sections (i.e. tubes) between various amps, though I'm not sure if the Deluxe has that option.
Both amps require a little bit of a learning curve to operate efficiently, which I basically equate to more practice time. Bottom line - both have great sounds. I guess it really depends on the type of tone you enjoying playing with most often, and how much $$ you want to spend. But value for the buck - I'd say the Vox gets the nod in that dept.
If you want an idea as to how the Vox AD50VT sounds, Robert Renman has some vid / sound clips on his excellent
http://www.dolphinstreet.com/music site. Many of our fellow forum members play the Vox AD30/50 VT amps, and they absolutely love them. Me included!
The Vox website has a number of demo sound clips, too. Here is the link for that page:
http://www.voxamps.co.uk/support/resources.asp?productCode=NEWAD15VT&groupCode=demo
The Fender website also has sound samples of the Cyber Deluxe. Here is the link to that page:
http://www.fender.com/products/cyber/cd/cd_sounds.php
My suggestion is this: If sound bytes won't allow for adequate comparison, and you don't have a local music store that carries either line of amps, both are available through Musician's Friend. That way, you can order one, test it out, and if you don't particularly like it - return it (they have a 45-day return policy). You'll be out the cost of return shipping, but at least you'll have an idea as to how the amp will sound through your own guitars. In my opinion, this is the only way to get a true feel of what those amps will do for your sound and / or playing. Amp "tone" is a very subjective issue, and what sounds good to one set of ears may not sound good to another.
Whatever way you do decide to go, I think you'll be pleasantly suprised at how "real" the tones in these amps sound, and amazed at the versatility these amps offer to today's guitar players. Good luck!