Advice on Specialized bikes

[Leaf in the Wind]

Hello all. I am getting ready to purchase my next bike. I am going with a 29er. I will use it for in town for packing groceries and casual riding as well as bikepacking in the back country and just for fun rides on the trails.
My last bike was a TREK mountain bike and I loved it. It was my first higher end bike. Now that I have learned a bit more about bikes, I would like to try another one. The TREK was great, but I still had to upgrade some things on it, to be honest though it may have been because I was riding it daily for over a year in all weather conditions more than 20 miles/day, so it may have just been wear and tear on it.
I went to a shop in Salsbury, MD and he showed me a bike called Specialized, and the model was the cross trail. I was wondering if any of you had any insight on this brand or model. From what I have read online they look like good quality, but most of it is coming from the company or its advertising.
Also, something new to me on bikes are the disc brake systems. The salesman seemed to think that it is the way to go now. Some models have both as disc, some had only one. In your opinions, what are the advantages, disadvantages of this brake system and should I go with definatley both wheels with it or does it not make a difference? 
Thanks everyone for your input.  Looking forward to hearing what everyone has to say. 

[AZTtripper]

Leaf, welcome to the forum. If it's been awhile since you looked at bikes there's a lot out there. The bike you mention is not a 29er from what I see. I only looked at the first two models but both had 38c tires. A 29er should have 2+ inches of tire clearance. These bikes look more like Cycle Cross bikes, think road bars, then mountain bikes. While these might make great commuters, I have a similar build, not really a single track trail bike. Sacrifice a little rolling resistance for a real mtb tire and you will have a much better trail bike, that you can still ride roads all day long.

Hope that helps.

Tim

[Leaf in the Wind]

Thanks Tim, I really appreciate the information. It is not so much that it has been awhile since I have been out in the bike world, as that I don't understand what all the numbers and lingo mean. I thought the guy I talked to mentioned that the tires were the 29" size, but it was something not real common on some platforms, but gaining more interest for certain applications. I am kind of a tall guy, so I was thinking it would work better for my height.
I was looking for my Specialized catalog that he gave me, and could not find it, so I may have had the model name wrong. The bike I was looking at was kind of a Mtn bike, but also good for cruising around the city streets. The tire was kind of a cross between a road tire and one that would be good for terrain. The feature I really want it to have is the ability to put cargo racks on it to carry camping/bike packing gear, or for panniers for groceries for in town hauling.
Anyway, thanks for the information, that will give me another area to learn up on, the tire sizes and what they mean. LitW