The Ferrari driver ran with the device for the first time on Friday, after teammate Kimi Raikkonen tested it on Thursday.
Force India Nico Hulkenberg was also against the device and labelled it as "horrible".
Four-time champion Vettel, however, is convinced drivers like Justin Wilson and Henry Surtees - who died after being hit in the head by objects during races - would still be alive today had the halo system been used in their cars.
"First of all, to go around is okay. You can see what you need to see," Vettel told reporters on Friday.
"I think we can improve the system in terms of aesthetics and also in terms of how much it's in your way, but I tested it as well in the simulator and I think we will see evolutions of it very soon.
"In principle I agree it doesn't look very nice but equally it helps increase the safety, it helps saving lives.
"There would be at least two drivers in the last four years there I remember that would still be around – Henry Surtees and Justin Wilson – if we had this type of system.
"I think it can be very ugly but nothing justifies not having these two guys around."
Additional reporting by Roberto Chinchero