Hi,
Well, an option can just modify the price and a characteristic will create a new "product entry" in the database.
Having too much variants could slow down your server and will require more memory to load a product page ; it will also generate bigger product page because all content of all variants have to be generated.
So, using characteristic is good if you want to change the picture or the description.
Using an option is better when the price modification is something fixed and you don't have to change an element for the product (like the product quantity, the image, the downloadable file, etc).
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.