I tried methotrexate but couldn't tolerate it very well but I've heard a lot of people say it's worked for them. I'm also covered in psoriasis have been for 5+ years am currently having the light therapy treatment and using a new thing called enstillar which is a foam that you spray on and it's really cold and then you rub it in and it's amazing I've been using it for a week and can see a difference. I'd highly recommend asking your doctor to try you with enstillar X

MTX worked a bit but I ended up on both MTX and remicade (infliximab)
That's rather a big decision you have to make at your young age.
MTX and acetretin are very damaging to a foetus therefore you cannot get pregnant while on it or for a year after. However if you need them take them and see.
MTX is probably the best choice. It has less sideffects .

edit to the above, it never worked for me.

i was prescribed methatrexate and had to sign waivers in case something went wrong. I asked about side effects and Dr. Duke in Ottawa said it will make your skin go thin. I thought he meant for the 10 weeks I was on it, not for the rest of my life. This drug changes the way your body makes skin, for the past 20 years every time I bump into a branch or a cat paw I bleed way too easily and way too much.

I was on methotrexate and it worked for about 10 years but then psoriasis came back and liver count changed so I had to stop taking methotrexate, sorry