Personally, I think about what happens if it develops a problem when deciding to purchase an item online or by heading to the shop. For small and inexpensive items, such as computer components, digital camera, TV aerials, etc., I buy them online. For bulky items such as washing machines, televisions, a laptop/PC, etc. and even helping a family member buy one, I feel it is far less hassle to head to the shop.
My brother already learned the hard way when he bought a 40" Samsung TV online. It arrived fine and worked great for a year and went on the blink. As he bought it online, he was given no choice but to mail it back, which meant packing it up (luckily he kept the original box) and organizing a courier to collect it, plus the postage cost of the repair centre sending it back to him. If he paid the â‚¬100 more to buy it in a local electronics store, there would have been far less hassle simply taking the TV back to the shop.
As for laptops and computers, after sales can be a major hassle when they develop a hardware problem or the computer is supplied with a wrong component (e.g. wrong processor, monitor, etc.). E.g. Dell support absolutely refuse to take back a laptop that develops a hard disk failure (at least from my experience), instead forcing the customer to run the recovery discs and repeat each time the OS crashes. For a computer with wrong components, they insist that the hardware is correct and that the customer is wrong. I've heard of similar issues for multi-function printers when they go wrong.
Finally for pretty much all bulky consumer electronics, such as fridges, microwaves, tumble dryer, etc., we buy them in the shop, mainly to check their appearance and again for ease of returning in case they develop fault. For example, the product size on the website can be very deceiving, since most product websites show all product thumbnails the same size, which is obviously not the case when you physically see the products in a high-street shop. Very seldom do we use the reverse approach, where we check out the item in the shop and buy it online.