Both Synthetic & Canvas tents have their advantages & disadvantages.
Synthetic tents (domes) are generally smaller and lighter to pack & carry, they dry quickly and are usually less costly than the canvas equivelant.
Under average use, you can expect to get around 5 years out of most good quality domes on the market.
Canvas tents, while being heavier & bulkier, have a lot of advantages over synthetics if you like your creature comforts!
They insulate you better from the elements, keeping you warmer in winter & cooler in summer, they last a lot longer - properly cared for you should get a good 20 years minimum out of a quality canvas tent, they are a much stronger option than most domes (steel frame & canvas verses synthetic & fibreglass poles), they can be easier to set up than some of the large domes (less peg points and ropes to worry about, as the frames are generally self supporting), they tend to stay darker inside in the mornings, so the kids sleep later (always a good thing for Mum & Dad!) & they are much more comfortable to live in than synthetics as the canvas (provided it is a good poly/cotton blend) breathes whereas synthetic does not.
There are some great 3 room canvas designs on the market now if you are looking for the extra space - Oztrail, DMH & Diamantina all have 3 room canvas designs available.
If you decide to go with the synthetic domes checkout the ranges from Coleman, Oztrail, DMH, Blackwolf & Roman. These all have good options to suit different purposes and budgets...
Regardless of which way you go, remember to completely dry your tent before putting it away - if you have to pack up wet, make sure you don't leave it for more than 24 hours before you dry it. Mould & mildew can destroy both canvas and synthetic very quickly if you leave them wet.