Is lifting suspension worth it ?

If you're happy with it I wouldn't bother.

The main reason for lifting is for bigger tyres, since you're not putting bigger tyres on....

If you haven't already take the anti roll bar off for abit of extra free articulation.

Ultimately lifting it won't of itself make the car any better off road other than to increase the ramp break over angle. reason being that it's the radius of the wheel/tyres that affects the clearance under the diffs nothing else. However fitting taller wheel/tyres also increases the ramp angle and the approach/departure angle too. Now on a standard jimny none of these angles are at all bad compared with land rovers mostly as a function of jimny being so nice and small. Where it all falls apart it trying as others have said, to follow a land rover in rutted ground because of the different track widths and the air gap under the diff. There are 2 ways round this issue first and most expensive is to modify your car so that it competes with a land rover for height and width but this is ultimately a futile adventure because it needs a fairly heavily modified jimny to match a stock defender and a defender with the same increased components would be almost unstoppable (by that what I mean is that a jimny on 33 inch tyres may be equally as capable as a defender from the factory but if you were to also give the defender a set of tyres 6 inch taller than standard the jimny would not be able to compete, it's a matter of comparing apples with apples not apples and anvils.) Or secondly and much more affordable is to modify your driving style and try to find routes to the same objectives more suited to the strengths of the jimny for instance narrower gaps where a land rover will not fit or softer ground where the jimny skims over where a land rover sinks to its chassis, there's fun to be found playing by your own rules.