Both vaccines block the human papillomavirus
Vaccinating all 12-year-old girls against the virus which causes most cervical cancers could cut deaths from the disease by 75%, a study suggests.
GlaxoSmithKline's Cervarix jab targets two strains of the human papillomavirus.
The firm's findings were presented at the International Papillomavirus Conference, along with a study on rival jab Gardasil from Sanofi Pasteur.
Gardasil was found to be effective on more strains of HPV than first thought.
For the Cervarix research, a computer model was used to predict the outcome of vaccinating all 12-year-old girls in the UK - a total of 376,385.
Applied to the whole of the UK on the basis of the latest cervical cancer figures, it would mean 262 deaths each year, compared with the current level of around 1,000.
The number of annual cases of the disease would also drop from 2,841 to 682.
The researchers admitted 100% coverage assumed in the study was unrealistic, but said even if 80% were vaccinated, the number of deaths would drop by 61%.
Cervarix works by targeting HPV 16 and HPV 18, the two most common forms of the disease.
It has also been found to be effective at targeting some of the other most common strains.
GSK is in fierce competition with Sanofi Pasteur, who are about to see their vaccine, Gardasil, granted a European licence.
Cervarix is still being developed and will not reach European approval stage for around another year.
The research into Gardasil, presented at the conference in Prague, the Czech Republic and funded by Sanofi Pasteur, found it provided protection against 85% of HPV strains responsible for cervical cancer - up from 75% shown by previous studies.
Dr Nick Kitchin, medical director at Sanofi Pasteur, said the results were "very promising".
Dr Anne Szarewski, clinical consultant at Cancer Research UK, said: "HPV vaccination offers great promise in terms of reducing the number of cases of cervical cancer and preventing deaths from it.
"Beyond the cases and the deaths, hundreds of thousands of women each year in the UK suffer anxiety when they have an abnormal smear result.
"The idea of finally being able to prevent cases of cervical cancer with a vaccine is extremely exciting."