Red dot info

Good morning,
 I own a Springfield RO target with I have just started shooting... I also own other pistols where I mounted red dot (vortex defender-ccw 3moa).

 In future I wanted to mount this red dot also on the range officer. 

However, I see that for bullseye they mount red dot type scopes... 
Could someone explain to me the reason? 
Do they have magnification or are they 1x?
 why does no one mount "classic" red dot (small with free window)

Thanks.
Giovanni.

The tube type red dots make reacquiring the dot easier, particularly in rapid fire and offer better protection from sun glare and moisture (rain, mist) when shooting outdoors. Magnification is not desirable although there have been comments about some older Ultradots having slight negative magnification.

Tube style is the classic layout (e.g., the old Japanese ProPoints, Aimpoint 3000 /5000). No magnification with red dot optics.

Big tubes (Ultradot, Sightron, Aimpoint 9000SC) usually have the best adjustment turrets and little-to-no parallax. You will need a slide rib (or an excellent frame mount) and scope rings to install a traditional dot. The mass is a benefit for recoil control and return-to-hold, but usually requires balancing the gun’s springs to ensure reliability. Long tubes also make it very intuitive to align the gun and optic in target.

So, for a one-handed precision sports—intuitive through-the-tube sighting, repeatable precise adjustments, better recoil management.

The next common optics you see at matches are micro tube dots (Aimpoint H1, Primary Arms Advanced Micro, Sig Romeo5). They usually mount with a single crossbolt, and don’t necessarily require a full rib. The smaller profile and mass means less spring balancing, but you end up with recoil that feels more like a metallic sights gun. It’s still a round tube, but it is a little less intuitive to align when compared to big dots.

Micro reflex sights (one lens, like the Defender, Trijicon SRO, Burris FastFire) are not ideal for precision sports, but some people make them work. The optics usually have a lot of parallax and very coarse adjustments. The absence of a tube means there are no visual cues for alignment.

you were very clear! now i have a very good informations to make choice!
thank you very much!