As mtsyganov suggested offering both can help users in making an informed decision, studies have shown that product videos do help in conversion.I recommend looking at this article which talks about a number of case studies of how product videos have increased conversion greatly. To quote part of the article
Zappos uses videos on a huge number of its product pages, and was one
of the original success stories in this area.
It found that sales increased by between 6% and 30% for items that
included product demos.
Ski equipment retailer Simply Piste used videos to demonstrate
products to shoppers. This video showed how much the backpack can
carry, the number of pockets, zips, etc.
As a result Simply Piste saw conversion rates increase by 25% on pages
that included video.
I also recommend looking at this post Videos for Landing Pages 101 which talks about how videos can assist in conversion and which type of videos convert best. To quote the article
A recent research report by Invodo said that 52% of consumers say
that watching a product video makes them more confident in online
purchase decisions, and another 52% said they are less likely to
return a product they have purchased after watching a video. Treepodia
says that video increases conversion rates, from 14% increase for
electronics to 113% for gifts.
The article also has to say about the type of video which converts best
How do you know which video format is best for you? Brian Massey, the
Conversion Scientist, has the answer. In a study conducted to measure
the conversion results of different video formats, Massey found that
talking head videos drove conversion rates of 3.2% vs. screen
capture of slides at a measly 1.6% conversion.