Shimano Claris vs 105? I'm planning to get my first road bike as I have been putting a lot of miles into my hybrid. Did a century last Sunday. Altogether I have done around 5k miles on my trek hybrid. So I thought getting a road bike isn't too bad an idea.

I went to a LBS and the mechanic told me it is better to get a Shimano 105 group set because it is a lot better than Claris. He mentioned how the transmission would be smoother. I'm NOT planning to buy a bunch of road bikes in future so in most cases this will be my only road bike even though I would keep my hybrid for my commute to work. 
So do you think it is better to get 105 over claris? 

Being a newbie in to road biking  would it make a big difference?
After doing a bit of research bikes with Shimano 105 is kinda expensive and getting a carbon bike with 105 is pretty much on the similar price range to getting the aluminum bike with 105.

So I'm wondering whether I should get a carbon bike with Shimano 105 or an aluminum bike with 105 or should I get just a cheaper one with Shimano Claris? 

Please let me know if I should be looking into some other groupset.
I've never used Claris, but I've used a bunch of different Shimano road stuff, from 8 to 11 speed, as well as some SRAM.

All other things being equal (which they never are), the more expensive Shimano groupset shifts smoother than the less expensive one. That, however, is splitting some really fine hairs. The shifting performance for modern brifters is nice across the board. In my experience, what makes a groupset good is how well you adjust and maintain it.

I vote for the Claris group. 8 speed is still widely supported and will probably remain so--you are unlikely to have a problem finding replacement parts (which are also much cheaper than 9, 10, and 11 speed parts) before you trash the whole groupset. 16 gears is also a pretty good range for any kind of riding.