All the bikes you listed are respectable.
Fit is more important than anything.
And get the bike you think you will need for next yr - so you won't be dissapointed if you love it and ride it more.
At this pricing levels - For more money in general you get the following.
LIttle bit lighter bike (components and frame)
Little bit smoother shifting and better braking.
Little bit longer lasting parts (won't need adjusting or replacement as often as cheper ones - therefore lower maint.)
A better front shock (maybe more bump absorbtion and more adjustability)
The bikes that you listed arenn't direct competitors.
You have compared a 350 bike to a 450 bike & a 500 bike.
Each brand has a 350, 450 and 500 bike....give or take a few bucks ...ANd a $400 bike in either of the 3 brands is very similar to any other $400 bike.
For example - multiple models in each line - low end competes with low end etc...the Yukon compares better to the Mojave 5.0 (not the 4.0).
In the 3 Brand you listed there are several choices all priced accordingly ($350 -600) .
Raleigh - Mojave - 2.0, 4.0, 5.0 & 8.0
Haro - Flightline ONe,Two, Sport, Comp...
Giant - Boulder - Rincon - Yukon
Buy from the Shop you like the best - and buy the best bike you can afford. My advice - don't spend less than $450 if you plan to ride on real Mtn bike trails - more is better mainly for the better front shock (Rock Shox) and better components Deore if you can afford it - Front Shox can cost $300 by themselves if you have to replace a cheap one later.
But if you never plan to leave the pavement buy the cheapest bike you like.
If you can affors $500 bucks I would call the 3 shops and ask for the best bike they can put you in for that amount (make sure they have your size in stock - they can discount bikes in stock more than special orders) and also ask about any last yr model closeouts - you may be able to get a $600 bike for $450 becasue it's last yrs model.
You are smart to buy 1st bike form a local shop. Ask if any servie come with it - some shops offer free lifetime adjustments. That is worth something.
If you have 1 of these in your city check them out too - www.performancebike.com - they sell the ironhorse & other brands like GT & Mongoose.