Trek 7.3 vs 7.4

It all depends on your wallet. I opted for the carbon fork and the better derailleur. But then I ended up buying a Deore front derailleur, Deore hallowtech 2 crank, Deore [censored], Deore brakes, Avid levers, carbon post, carbon bar ends, Selle seat, Vittoria 25c tires, Wellgo magnesium MG-1 pedals. So I ended up buying a $1200+ bike... If you plan on leaving it as is, I would say definitely go for the 7.4 for the extra $100. I'm just nuts and love to upgrade the [censored] out of my bikes like I did with my Specialized Crossroads. Paid $600, have $1000 into it, and still not done. The 7.4 is great... I love it.

Test rode both the 7.3 and 7.4 this morning.

I would say the 7.4 has better shifters but not by much. And I really noticed barely, if any, difference in the way they rode (the carbon fork on the 7.4 over the 7.3's standard fork).

I will probably test ride the 7.4 Disc when the store gets one in, just to see if the brakes are that much better. Originally I was thinking discs so that riding in rain and snow would be easier/safer. But I am considering keeping my old mountain bike Fuji just for bad weather biking, that way I am keeping the new Trek out of wet weather. If I do that, regular brakes would probably be just fine.

I think you would be fine with the V brakes. I have Deore V brakes in my 7.4, and they stop better than My Avid BB7's did on my Marlin.