Omega or AirVenturi or Benjamin

They are all the same for the most part. Try to buy one with BOTH gauges. Tank pressure and fill pressure. 

I had 2 Benjamin tanks. They looked nice but both were returned because of fitting leaks. The valve on the Omega looks like it is heavier duty/better quality than the valve on the AV unit, which looks a lot like a Ninja valve. The Omega Gauge is bigger, easier to read and probably more accurate than the smaller gauges on the AV. While it is convenient to have a separate tank gauge, you can also just plug your fill hose or cylinder valve with a deadhead plug and it will do the same thing. Also, if you accidently knock the tank pressure gauge off, you can have a real problem.

You might also want to look at the small Airhog tank: https://www.airhog.com/tank-sets/178-14-cuft-small-tank-set.html It has a valve made by Midland Diving, which is very good quality. I have one of these tanks sets and a second larger AV tank with this valve and it is really easy to regulate and bleed pressure. You can easily throw the small airhog tank in a backpack.

The other thing you may want to check is whether the valves or fittings are restricted. If your friend has an unrestricted fill set for filling the cylinder, than you can use a restricted valve and/or fittings on your set, which will make it easier to control the pressure when filling your guns. You can fill a cylinder with a restricted valve/fill set, it will just take longer and the compressor will have to work harder. Likewise, you can fill a gun with an unrestricted fill set, however, it will fill very fast from a 4500psi tank and will be more difficult to control.