Woodysom - The Guide and Hurricane are "Guidance" and the Omni are "Stability".
Although it's something of a simplification, essentially, the Guide and Hurricane will help counteract most mild to moderate over-pronation, whereas the Omni has more support usually used by people with moderate pronation or sometimes more.
Whilst the stability of the Hurricane is similar to the Guide, it has more cushioning so will feel more plush and luxurious underfoot and around the upper.
I appreciate that this isn't a Saucony question, but hope you don't mind us offering an answer.
Wear on the inside of the heel is often due to the foot rotating inside the shoes (and rubbing through the fabric at the point with the greatest friction – often the nobbly part of the heel/calcaneus). This can be down to poor fit (sometimes remedied by lacing) or possibly the shoe being too-supportive under the arch which in turn encourages the foot to move without the shoe.
Overall, somewhere between 350 and 600 miles is about accepted for the life of a shoe, but you might want someone more independent than me to back that up! The range is so wide because of the impact gait, running surface and suitability will play on the lifespan.
Also, for those looking at the outsole of their shoes as a guide to how much life left, remember that the outsole is generally carbon rubber and is just about the hardest-wearing component in the shoe. IT's the white midsole that will compress and deteriorate first. Keep an eye on that for creases and the feeling of "flatness" when running, particularly on hard ground.