Ok, I have looked at the D3100 with the 18-55mm, but whats the difference between that one and theCanon PowerShot SX30 IS 14.1 MP Digital Camera?
pros and cons?
Well, there are plenty of features that could potentially be compared. But, the main physical difference is that the Nikon D3100 is an interchangeable lens DSLR, while the Canon PowerShot SX30 is a point-and-shoot. This obviously begs for further explanation.
A D-SLR camera can accept a variety of lenses, from super-wide angle lenses to super-telephoto and everything in between. D-SLRs
typically offer creative flexibility and image quality that trumps point-and-shoot cameras.
A point-and-shoot camera generally can only use the lens that is permanently attached from the factory. For this reason, the attached lens is designed to be very versatile. The higher-end point-and-shoots, for example, oftentimes feature enormous zoom ranges that just aren't available in a single lens for a D-SLR.
There are upsides and downsides to both.
A point-and-shoot is the ultimate in portability and ease-of-use and will perform well in most situations that you come upon. The downside is that the image sensors in these cameras tend to be smaller than those in D-SLRs, meaning that you are taking a hit (albeit sometimes a tiny hit) in quality for the convenience these cameras offer. Image quality also suffers a tad bit because its not easy to engineer lenses that can offer a 35x zoom range (in the case of the Canon PowerShot SX30) without making compromises in terms of how it performs.
As mentioned earlier, a D-SLR uses interchangeable lenses that rarely exceed 10x zoom... usually much less ('prime' lenses, for instance, don't zoom at all). These lenses are designed with a limited focal range in mind and will generally perform better overall than that of the point-and-shoot. The image sensor is usually better than those of the point-and-shoots, as well. So, from the get-go, image quality is amongst the main distinguishing factors. Of course, the D-SLR offers compromises of its own. For example, you'd have to carry around 2 to 4 different lenses with a D3100 to cover the same range of focal lengths covered by the Canon out of the box; you'll also have to manually change these lenses whenever you want to change your focal length from one range to another.
This doesn't even come close to a complete comparison of the two designs, but it covers some of the most fundamental differences between the D3100 and the SX30. You'll really need to decide which package suits you best by doing a whole lot of reading and maybe trying to visit a camera store to actually pick up the two different cameras in-person and see how they differ.
Suffice to say,
very few people ever "went pro" with shots from a point-and-shoot... a fact that many might argue to be irrelevant, but which stands as a basic indication that D-SLRs are widely-accepted as offering the image quality and creative flexibility that people need if they are making their living taking photos. You may very well have no interest in selling your photos, but I mention that simply because the D-SLR is almost universally considered the "superior" camera for those that are sincere about their photography.
That being said, most "pros" don't use entry-level D3100s either. Nonetheless, if photography is something you feel you'll pursue for a good deal of time into the future, I would suggest the D3100 over the SX30. My viewpoint is: you might as well start getting used to a genuine D-SLR now. If you buy a better Nikon down the road, you'll still be able to use whatever lenses you've accumulated.
But choose what suits you by
doing plenty of research. Nobody here can effectively make the decision for you, even if we can be of some help.