PTCL - ADSL vs VDSL

I requested PTCL to install a 20 MB high speed broadband connection at my house in DHA Phase 2 Karachi

PTCL has now told me that a 20 MB ADSL connection is not possible in your area but they would give me a 8 MB VDSL which would ensure a consistent speed.

I am a novice in this area. Can someone decipher this for me. Should I opt for a wifi connection instead.