In my opinion, a good steel door can offer a lot of protection. On any door thogh, you'll need to properly secure the jamb. One manufacturer (Stanley?) offers a steel plate that goes almost the full length of the jamb on the latch side and it attaches to the framing.
Personally, when I install a door I foregoe the steel plate and I use 3" or 4" screws through all hinges and I take up the space in the back of the hinges with plywood or 2x4 ripped to fill the exact space. Glue this in place and screw through it. I do the same on the latch side. It takes a long time to install, but it is very secure.
Having an out-swing door (with proper hinges) will be stronger (when being kicked in) than an in-swing door, so that might be something to think about.
A good lock is also important. Don't go all out armory style on the door and then put in a Kwikset or EZSet lockset on the door. You get what you pay for when it comes to these things.
A lockable storm door can offer a little more protection in conjunction with a good solid door. It's something more to go through.
If your door has sidelights or glass, then don't go in vain trying to secure it. They have an easy way in already and will just break that and reach around and unlock it.
Get a protected by xyz security sign and put it in your yard. Also get stickers for your doors/windows. Even if you have no security system, it is a good deterent. Beware of dog sign never hurts either. Anything you can do to make them just move on to the next house helps.
Hope this helps.