Thinking about a new road bike.

Assuming you're not intimately familiar with my situation, I just started riding this July. Bought a new Raleigh Venture 4.0 - a "comfort hybrid". I feel like I am past it. Dug out my 35+ year old Ross Gran Tour II and decided that what I really want is a modern road bike, but still with the ability to ride on the occasional few miles of "dirt road".

I've been doing a lot of surfing etc and found that an LBS has a couple of options that appeal to me. I haven't talked to them yet, but it appears neither are on site, but available from the factory.

The Raleigh Roker Sport is a full carbon leftover '16 bike, and heavily discounted. It appeals to me because it's light, full carbon, has larger tires and a 1:1 low gear (I live in hilly Vermont).

However, the Raleigh Merit 3 has a 105 groupset (instead of Tiagra) and is $400 less and not even 2# heavier with an aluminum frame and only carbon fork. Low gear is a 1.0625:1 low gear, which is just about doable for me right now, and I anticipate it being "within capability" in my reasonable future.

I feel like the Roker Sport is more in line with my type of riding, but why does it have Tiagra instead of 105? If it had 105 it would be just about a slam dunk.

I can read specs all day long, but I feel like there are some fundamentals that I have no clue about. Why does the $2500 list price bike have a Tiagra groupset while the $1400 list bike has a 105?

I will add that I need a pretty large frame, and there seems to be very little excess inventory of bikes in my size, hence my initial resignment to just ordering a new one next spring.

Any thoughts appreciated.