I would store them in a standard string eVar personally.
Events are counters... just like Page Views, except you are choosing something specific to count... event when you use a "Numeric" event, you are just telling the counter to increment by a specific number. For example, let's say I am using a simple tracking for impressions of recommended content, on page A I have 3 so I would use my numeric event to pass 3 (event1=3), and I have another page that shows 5, so on that page I pass 5 (event1=5)... if I look at my data, my event will show 8 impressions.
Numeric eVars, despite the name, still store the values as text... the real benefit to these is being able to use the +x designation... so let's say I want to track the number of product pages a person visited, but I also want to be able to see on which depths the person add to cart. On my product page I would use eVar1=+1 (the first products will be 1, the second will be 2, etc), but when I correlate my product name to eVar1, I will still see "1" or "2" respectively on the products, and with attribution, if the user adds the product to the cart, I will still see the corresponding "1" or "2". However, the data is still stored as a string...
Neither of the above use cases seem to fit your needs....
The big question is, do you only need that information on the Product page, or will you also need it on the Cart page (for multiple products) or on Purchase? If yes, then you will want to use Merchandising eVars and pass them in the Products List notation. Some of these you may want in all places (price, discounted price, available quantity, etc - and these values could change by the time the user is on the cart or making a purchase, so you would need to grab the up-to-date information for each product - you wouldn't want to rely on attribution from when the product was viewed), others you may only need on the product pages (number of reviews, etc - this may change by the time the user is on the cart, or making purchases... but since they can't see if, do you really need it at this point?).