So i'm looking to buy my first non box store bike but i'm wondering what sort of bike I should purchase, My goal is weight loss and cardio for my workout regime so I ride on the road with lots of hills, would I be best off with a road bike which I'd travel faster on or a heavier but slower bike like a mountain bike. Would I get the better workout on a road bike or mountain bike given distances and terrain is the same.

max of 500$ or so is my budget, college student

You on a road? Ride a road bike. You on a mountain? Buy a mountain bike. You sometimes on a road, sometimes on a mountain? Buy a Giant Anyroad and split the difference.

Sounds like you need a road bike. Problem is, you won't find much of a road bike for $500, unless you buy something used.

Check both Performance & Nashbar for their close out, both run sale constantly.

how good is a roadbike for roads that have lots of cracks, potholes etc that may or may not be avoidable? do I have to really worry about ruining hundreds of tires due to poor road condition? I was looking at Adventure 3 - ADVENTURE - FITNESS - FITNESS & URBAN - BIKES - 2015 as a middle ground, opinions on that?

The Cannondale Adventure is more of a comfort bike. You have the right idea with a hybrid, but the type I'd recommend is something like the Raleigh Cadent. Exactly built for the purpose of fitness on the road. It's not that road bikes can't handle rough roads, it's just this one will be easier on them. Don't think the front suspension on hybrids is necessarily for terrain. It's more often for comfort.

+1

I wouldn't buy an MTB, unless you plan to ride some actual trails, try out some downhill, etc. You'll be more efficient on a road bike or a cyclocross bike with beefier tires, if road surface is poor. The Raleigh Cadent and the Cannondale Adventure are both good options, but I also dislike the front suspension on the Adventure.

If you are asking my opinion, the above bike would not be on my short list. It isn't something I would enjoy riding all that much, though others may not agree. IMO, it is more of a comfort bike than a fitness bike. I ride for fitness and exercise at least several times a week in the spring through early fall riding season. My wife rides almost as much as I do. We both ride bikes with drop bars. I ride a light touring bike with 32 mm tires. My wife rides a road bike with 28 mm tires.

I can relate to roads with cracks and potholes as our Wisconsin winters are brutal on roads. The answer isn't necessarily a soft comfort bike with a suspension fork, though you might choose a larger or harder wearing tire than you might otherwise. You ride around or jump over road debris and/or potholes or ride softly over them.

I am liking everything more about the Cadent 2, including the disc brakes. Super close to OP's budget.

Raleigh Bicycles - Cadent 2

well, time to find a shop with the cadent and give it a ride and start saving up

is the cadent 2 THAT much better than the 1 to justify the extra $ ?