Well I guess I can list advantages and disadvantages for both.
Grass: Grass types tend to have access to useful, exclusive support moves, such as stun spore and leech seed. They also resist water type attacks, which is really useful when switching into a water type attack. However, almost all water type Pokemon learn ice type attacks, which are supereffective against grass types, and some can even use fire type attacks and poison type attacks to handle grass types. Also, grass is resisted by seven types, only hitting three supereffectively, though these three are common. They are also weak to five types, with all but poison being common offensive types, especially fire and ice.
Electric: Electric types don't resist water type moves, but only have a single weakness, to ground, a type most water types don't carry. Electric type moves, such as thunderbolt and wild-charge, are also very powerful and can dish out a lot of damage, further augmented by electric types typically having good offensive prowess. Electric type moves also get great coverage with ice type moves. Really the one issue electric types have with water types is water/ground types, which are immune to electric type moves, while no grass types are immune to grass moves (except for those with sap sipper)
In the end, both types have offensive and defensive advantages and disadvantages. The most important thing to consider is what your team will work well with, and whether that's a grass or electric type I hope this helps.
*I personally use Ferrothorn as my water-counter, as it has great bulk, is neutral to ice type attacks, hits hard with power whip. Here's the set I use.
Ferrothorn@leftovers/rocky helmet
Curse
Power Whip
Gyro Ball
Ingrain/Bulldoze
