A quad beam is the coolest.
The guys that use them are the first ones to make a contact - and the last ones still talking . . .
That is what they say about it.
I had a 2 element quad years ago.
They are light, need only a TV rotor, choice of horizontal or vertical polarization, decent forward gain with decent side/rear rejection, and inexpensive to buy and set up.
No real down side . . .
A horizontal beam will often hear things that a vertical won't. Or vice versa. Signals can arrive at your antenna with either a vertical or horizontal polarization after it has made several bounces off of the ionosphere. I get far more contacts on the horizontal beam due to a quieter receive, as this helps immensely too.
Doesn't hurt to use/have both.
That is, if DXing is your thang . . .
Yeah...I got burned on 2 used rotors I bought....one off ebay and the other off a local....also a control box off ebay.....the only way I would buy a used rotor again is if I seen it work.....kinda turned me off of wanting to put my beam up....for the time being anyway.
Some of the guys around here claim that once you go flat....you won't go back....one guy in particular preaches flatside....and he does do really well at talking skip.
If you want a nice Ham IV go to Smokey's CB Shop. He cleans them up and rebuilds them and has a few in stock for an excellent price, excellent quality! I bought a rebuilt Tail twister from him in 2000 and it plays beautiful to this day.