Upgrade laptop gpu is waste of money . think spend $100 for to get extra 2fps. Disadvantages of branded system: Branded systems only give 1year warenty,Assembled system give 3years warenty (2year extra warenty compare to branded).
branded systems give limits for users examples: 1:limited sata ports ,2:low space for extra hdds ,3:upgrade processor also not supported (many processors) because of branded system bios. 4:upgrading gpu also not supported (many gpus )because of branded systems psu and bios limitations. 5:if u r linux user don't spend money for ms os and softwares. etc.....