Are spears something special over the shield and hand weapon? You get a parry save with the later, what special benefits do you get with spears?
Depends on the rulebook. In basic 8th you get fighting in an additional rank when not charging, but only when fighting in the front. This makes spears a better offensive, but worse defensive option. Funnily enough for the longest time I assumed that Spears also required two hands to use, making them a much worse option. In 9th Age they've got a couple of additional buffs, namely armour piercing and quasi-killing blow against cav and similar big things. In 9th Edition, they grant an initiative bonus when charged in the front. This by itself is unimpressive, but considering that supporting attacks got removed, it's damn important. So yeah, Spears are a more offensive choice and better if you've got the rank and file to support the additional attacks. Shields are defensive and better with smaller Saurus units.
In 8th it's generally better to keep the shield/sword because the models you save will keep you going longer and benefit you longer. Spears grants a situational bonus, which you lose the second you lose models in the third rank. Due to I1 this is an issue. Spears can work, I suppose, If you build your magic around it.
I'd only recommend going with spears if you plan to make the unit BIG. Large numbers of troops to soak up damage and maintain the extra rank advantage. Personally I usually opt for sword & board.
In every edition at this point (except AoS, but i do not care for nor acknowledge AoS) sword and board is the better option, for different reasons.
In AoS it's more or less the same. Spears are better for large units, while for less than 20 models swords are more efficient.