The harrier’s primary mode isn’t hover, it’s fixed wing flight. If I were to guess, I would say that it would not do well against fighters or helos.
The Harrier has the 2nd best air-air kill ratio. The first is the F15.
https://migflug.com/jetflights/the-combat-statistics-for-all-the-aircraft-currently-in-use/
The Harrier is designed as a BOMBER; the F15 is designed as an Air Superiority FIGHTER. In exercises, the Harrier bomber beat the air superiority fighter 3:1. That’s like saying my delivery van can beat your Ferrari off the line 3:1, let’s see how your Ferrari does in delivering a ton of Amazon boxes.
https://freerepublic.com/focus/f-news/1342535/posts?page=78#78
excerpt from a magazine, “NATO Warplanes”, from 1985 and has the page #37 on the bottom. ... the front has a tear off which includes a table showing the Kill Ratios of the Sea Harrier vs. Other aircraft. Here’s the Table:
Sea Harrier Success Record in Combat Engagements During Peacetime Exercises
(Figure 3)
VENUE ADVERSARY KILL RATIO
(Sea Harrier Wins: Adversary Wins)
Decimomannu 81 F15 & F5E 12:4
Decimomannu 83 F16 31:14
Alconbury F5E 3:1
NATO Sea Exercise F14 3:1 to 10:1
United Kingdom F4 10:1