Neither HR or GH are my favorites in Bangkok but they are both good enough to be part of a rotation of where I stay as they have their own distinct pros and cons. The knock on GH is that the hardware is quite aging by now, far more than the vast majority of newer hotels in the city (not only in comparison with HR). I remember bathroom tiles coming off in small pieces in one of the rooms I had. In addition, it's more difficult to get a suite upgrade at time of check-in at GH due to small number of suites and if you don't get a suite then there is no room type more spacious than entry level (unlike at HR which has Deluxe rooms as a reasonable plan B). At GH if you don't get a suite, you can pretty much expect that your upgrade will be very modest (higher floor, etc.) and offer little value.

Since I care about both having extra space and having newer hardware, HR has some advantages despite not being luxury. For GH I consider it almost a must to use a Globalist suite upgrade ahead of time as I don't want to be stuck in the entry level rooms there. It's rarely a concern at HR.

In the same line of thought, for a stay where I am willing to pay for a suite rather than gamble on an upgrade, I would do so at GH ahead of HR.