Every country has their stores with their own big problems, mate. For example, here in Brazil, the largest hardware store, KaBuM!, was bought out by the country's largest department store chain - Magalu - and suddenly, their prices weren't the nicest and they adopted some pretty dodgy business practices. RMAs became difficult and highly scrutinized, availability of parts was no longer the best, amongst other things. Pichau, the largest "independent" computer store in the country, will happily sell you anything and then figure out how, what and when they'll ship it to you. Almost every single one of my purchases with them was heavily delayed. Need to buy from them scheduled in advance, and their RMA procedure is complete dogshit (I've had them hold me up for 2 weeks over legal maximum period, honestly I've had RMAs that took 100 days to process with these guys).
TerabyteShop's got less and less stock on relevant and interesting things every time I look. Patoloco's stock is extremely restricted and they generally cater to lower income market segments, so they rarely carry high-end GPUs and whenever they do, it's basic models. WAZ's prices are generally the highest in the country. Amazon.com.br is still largely stuck in the bookstore days of yore.
I tend to buy from Pichau whenever I can, mostly because they carry the fancy things I like. But just as I said before, their shipping times are horrid and if you need to RMA with them, you're screwed.
Generally, my take is this:
1. Is a shop reputable and trustworthy? If yes, proceed to step 3. If no, proceed to step 2
2. Is the product available from a marketplace with an escrow service? If yes, proceed to step 3, if no, there is no deal
3. Are purchasing conditions (price asked, shipping time, forms of payment accepted) favorable? If yes, we have a deal, if no, there is no deal
I will count as a negative websites that engage in deceitful or over the top marketing, but these tend to be relatively rare and generally, in conflict with point #1 (trustworthiness of a store).