Nikon d5500 with 18-300mm or mirrorless?

I have never owned a dslr before but i have clicked a lot with my 20 year old Olympus (manual lens)
Now i want to try the combination Nikon d5500 with 18-300mm f/3.5-6.3G lens. I prefer the zoom lens so that i don't have to change lens very often. If i ignore low light conditions, is this a good combo to buy? Any other dslr combo that i can go for in this budget?

Or should i go for a mirrorless cam. I want something at par with my dslr combo if i go for this option. Any suggestions?

Mirrorless cameras still only account for about 20% of all fully adjustable SLR cameras and they have a few drawbacks.

* since they do not have an optical viewfinder, two things happen.
> when shooting sports, there's a slight delay from when the image strikes the sensor and the electronic viewfinder actually "sees" the image. This means that you sort of have to anticipate the shot before it happens to hope to catch the player at the "right" time
> the electronic viewfinder uses quite a bit of power, so the number of shots you get from a fully charged battery is much lower than cameras with optical viewfinders like the D5500. The Sony A7 with 36 mp sensor can shoot up 340 shots on a fully charged Li-ion battery vs the Nikon D810 with a 36 mp sensor which can shoot up to 1200 shots on a fully charged Li-ion battery
* currently there are not nearly as many lenses available for mirrorless cameras as there are for ones like Nikon. If you look on the Sony website, you will NOT find a 18-300 mm zoom lens

The 18-300mm zoom lens will have poor corner sharpness through most of that range.
http://slrgear.com/...25/cat/all

18-300 lenses involve a lot of compromises and typically they have one sweet spot and that will not be at the far end. They cause extreme barrel and pincushion distortion which, in many modern cameras is dealt with by onboard software. They deal with the very dark long end of the lens by using higher ISO.
Mirrorless cameras are generally not robustly built and eat batteries.

So, if you don't want to change lenses, would you be better with one of these Sony RX10 which has an 8.3 x zoom and a constant f2.8 aperture throughout
http://www.photographyblog.com/reviews/sony_cybershot_dsc_rx10_ii_review/

For your purpose, yes, that is already a good combination. No, you won't be able to match that with mirrorless.