A Makeover About to Happen

I'm sure you knew a furniture makeover was imminent after I shared my obsession with staring at before and after furniture pictures (found here).  With John on Spring Break, the weather looking warm and sunny, and many kind and encouraging comments, I figured I needed to take a deep breath, put on my big girl panties, and grab a paint brush.

I'm starting small on two side tables in my living room that I have hated since the moment I shoved them into my car.  Several years ago, when John and I moved into our first apartment together, we didn't have any furniture whatsoever. Nothing, nada, ziltch.  So, I went craigslist crazy and bought the first thing I saw in all categories.  These tables were the first of the mistakes.

I am planning on painting them heirloom white, which seems to be the diyer's ideal paint.  I've wrangled my husband into sanding them and I'll begin painting them tomorrow.

I do have some questions:
     1. Oil-based primer or water-based primer?
     2. Should I try and cover up the groves with wood putty or leave them be? I really don't like the plank look and would enjoy a smooth table.

Wish me luck, I'm off to Home Depot.