I use shopee because compared to lazada, most of the same items (from the same sellers) are posted with cheaper prices. For example, a toy dinosaur costs 399 on shopee, but when compared to lazada, it costs 499. And this is from the same seller.
I also, always get a free shipping voucher as well as discounts for using shopee pay.
Disputing refunds was also easy since I use shopee pay.
It is good to note though that when it comes to MDF furniture, it looks like lazada has cheaper prices.
Shopee customer service sucks though. So if you encounter something that is not usual in their system, you'll just get frustrated.
Lazada customer service (as far as I remember) has always been easy to deal with