Laptop or Desktop?

A laptop with a minimum confing to run Photoshop CC 2017: 128GB SSD, 8GB RAM, IntelCore i5 or equivalent AMD and a dedicated graphics card 940M or better with min 2 GB video memory. You can choose from different manufacturers and I recommend ASUS, because it is easily upgradable - for example, I've increased the RAM by myself and you also find lots of tutorials online.

Does SSD must? what happen if I use 512 GM normal HDD?

I would suggest you to have a desktop if you are a designer and want to run PS of any type. Desktops are of low cost as compared to laptops and you can get a good config desktop in low price.

At home I mostly use my desktop but sometimes my notebook. I prefer the large dual screen setup of my desktop to the small notebook screen.

Performance wise my notebook is actually much faster. The notebook is only a few months old (Core i7, 16 GB RAM, SSD) while my desktop is a few years old already. So sometimes I use the notebook for advanced operations if the desktop doesn't cut it.

Always keep that in your mind that for graphic designing purpose individual should always use desktop. Desktop usage makes you addict to it and you always gona get the best result on desktop.

I prefer desktop

You can use both. Professional designers should constantly study on the desktop. But if you are interested to use a laptop then the best laptops are HP Envy 13-ab016nr, Dell Inspiron 5567, MSI GV62 8RD-200