Which route to gain posession?

Possession - Section 8 and Section 21

I have a tenant who is significantly in arrears with her rent and I have served her with both a section 21 notice (to expire 28 March) and a section 8 notice for rent arrears.

I am in the process of drawing up court documents but note that the advice re fault based posession is to get a solicitor involved.
I'm wondering if I should just wait and go down the s21 route and be assured of a posession order.

The tenant I believe is probably depressed and unable to cope financially or otherwise. I doubt she would challenge any submission, nor would she turn up in court.

I have been unable to get any response from her for some months now and am not entirely sure if she is even still at the property.

Any advice would be welcome.