OP, guess you're just trying to get into your first road bike, eh?
While I will never claim extensive expertise in bikes, I did work as a mechanic/sales/everything guy in a shop for about a decade...ran the shop for about 5 years. Sold Trek, Cannondale, Schwinn (after their first bankruptcy), GT, Litespeed, Santana, Giant, Klein, among others. So, I have formed opinions and you can take them for what they're worth.
But understand, when you talk road bikes, you are entering a world that's comparable to the audiophile sphere, meaning opinions are widely varied and sometimes really unfounded.
First, realize there are lots of good bike brands. To my mind, the trick to buying is to find a bike shop that'll spend time with you. If the shop won't spend the time you feel is necessary to make you feel comfortable, answer all your questions, leave. They're just out for the $$ instead of making sure you fit the bike and are put on an appropriate steed.
Second, set a budget. Don't go into a shop without a definite line in the sand drawn as to how much you want to spend...it's very, very easy to get upsold and upsold needlessly, especially being new to the roadie arena.
Third, don't focus on just one brand. Bike companies do have philosophies about how a bike fits, so try several brands until you find a brand of bike that feels comfortable under you.
That said, some things to realize and look out for when making your decision. Giant is the largest bike manufacturer in the business, considering worldwide sales. Chinese brand, controls most of the Chinese frame making factories. Their factories make most of the Chinese made frames, no matter what brand is plastered on the downtube.
Trek, Specialized, Cannondale....all good brands. Keep in mind Cannondale of today is NOT the Cannondale of the 2000's. Due to Montgomery's obsession with satisfying his boy's every whim, he bankrupted the company when he tried to enter the 4 wheeler /ATV market. Interestingly, you can time his kid's aging by what weird thing Cannondale was building at the time. Kids bikes when the boy was very young, only lasted a few years, BMX bikes when the boy was of that age, then ATV's when the kid was older. Each time, the product was only built while the kid was interested, then dropped. Sad, really.
Anyway, I'd not get hung up on brand and buy instead by shop and fitment/comfort. There'll probably be a brand that fits you better than others.....and then you've found your bike.
About components. The aforementioned Mavic wheel issue really isn't an issue these days. Sure, back in the '90's when Mavic started out the bladed spoke thing, it was something to at least watch out for. But these days, with Mavic, Shimano, Easton, et al, all producing their own proprietary wheelsets, a good shop will have the appropriate repair parts....and any shop worth anything will have something to repair your fancy wheels, if that's where you end up.
I'd be more concerned about looking out for Campagnolo components myself. While Mavic/Easton/et al wheels abound, Campy parts don't. I'd stick with looking at Shimano equipped bikes, at least for your first bike. And since you're probably not going to be shopping the $2k and above price point, Campy really won't be an issue.
Like I said, shop the shop first. If they cannot give the time to make you feel comfortable with the experience, take time to answer each and every question, put up with you coming back a few times before buying, move on. If they can't spend the time making you comfortable while selling you the bike, what are they going to be like when it comes time to fix/repair it?
Good luck and enjoy riding.