"Wounding (with) intent" is short for "Wounding with intent to do grievous bodily harm" and "gbh (with) intent" is short for "causing grievous bodily harm with intent to do grievous bodily harm".They are under section 18 of the Offences Against the Person Act (of 1861, which date explains the rather archaic language used )
The difference is technical'.Wounding means causing a wound, an injury which pierces the skin. "Gbh" is any really serious bodily harm. It's possible to cause someone really serious injury without cutting their skin. The 'wounding' version is usually used when the weapon was a knife.
The intent is what matters. In both cases the intent must be to cause really serious harm, the difference being only in the way that intent is carried out.
Both versions are punishable with the same maximum (life)