Don't go for Asus gaming phones as they have a lot of hardware issues, if you wanna reward that employee with a gaming phone just give him latest Black Shark phone or Nubia Red Magic 6s pro as they are durable and made of quality materials unlike Asus which tend to show issues in just few months and you have to keep running into their service centres.
As far as ASUS is concerned, the ROG Phone 3 is a lot better than the ROG Phone 5. It feels like the ROG Phone 5 was rushed to market as it has quality control issues the 3 doesn't. For example, the 5 can be bent pretty easily, whereas the 3 can't:
(Thanks to Danishblunt for pointing this out before). The ROG Phone 5 uses the Snapdragon 888 processor, which is poorly optimized (gets too hot, etc), whereas the ROG Phone 3's Snapdragon 865+ is a finely tuned version of the 865. Though, that isn't so much ASUS's problem as it is Qualcomm's. ... I think the only advantage of the 5 over the 3 is it has a headphone jack (amusingly, the 3 was the only ROG Phone to skip it). Personally, I've been very happy with the ROG Phone 3 since I got it last January. Is it perfect? No, but I haven't had any huge issues with it. I can't comment on phones from other manufacturers (Lenovo, Nubia, etc) as I haven't used them.