I would imagine you would get an improvement in stiffness - no wobble from side to side.
The trade off would be considerably increased road noise.
Also it may place extra stress on other parts. ie: the bushing is currently the weakest part and is designed to fail - if this is made much stronger what is the next weakest part? Could be more expensive to replace.
For just road use I think it is probably better to stick with stock bushes - they are very cheap. If you definitely want to upgrade, or if you are thinking of doing a DIY repair then I would go for powerflex (or similar) 2 part bushes. They will be easier to fit and are made from a stiffer plastic that should last longer.
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