There’s no perfect radio. There’s no best radio for SOTA. They all have different strengths nad weaknesses.
FT817 is cheap secondhand, it does HF and VHF competently. It’s tough and they seem to stay working overall. There are loads of add ons.
It’s expensive new, the internal battery is a joke, the usability is so-so especially in the field wearing gloves. It has high current consumption on RX.
But it’s the only all mode 160m-70cms compact radio.
The KX2 is a significantly better HF radio but doesn’t do VHF/UHF. It’s much more expensive than an 817/818 new.
So if you are a relatively new ham wanting to try HF and protable operation, buy a secondhand 817 and an external LiPo / LiFePo battery. It will be massively more than competent for a newcomer and in a few years time you can look at selling it and buying something better such as KX2. If you look after it, you’ll not lose anything over a 3 year period. Or you can keep it and buy something extra anyway because more radios means more fun.
Remember, the radio you actually have and use is significantly better than all the radios you want to own!