It is harder on the bearings, but probably not so bad as to worry about it unless you do heavy loader work on rough ground, at a speed other than very slow. But, doing my usual though experiments (make it much wider, much narrower, much heavier, much lighter, much faster, much slower) I come to the following conclusion:
Unless you can make the front very very wide, and be assured the axle won't simply break, due the to pivot point, a wide front axle will not add appreciably to stability. It will give the perception of increased stability, but it will not help much against a roll over.
The rear axle is key, and wider there is definitely a help, but even so, ballast is still the key.
