Do you get a lot of rain? Do you have expansive soils (high clay content)? Do you see movement with fences, and/or ground cracking when the soil is dry? Do houses in your area have cracking in the exterior stucco walls, interior plaster or gypsum board walls, concrete slabs, etc.

If the answer is yes to any of these, getting water away and keeping it away from the exterior foundations is a big deal. Gutters, downspouts and diverters help accomplish this (along with positive final grades).

I agree that gutters and downspouts, if not carefully installed, may not always look the best, but they can be done in unobtrusive ways in many cases.

The question to install or not to install is often one of "pay me now, or pay me later".

Yep, your chosen architectural guide eschews gutters as clutter. Form before function. Witness their fondness for butterfly roofs that originated in California deserts. If you choose that route, consider longer than typical overhangs and appropriate grading.

Thanks, Virgil. To answer your questions (which may have been rhetorical)...a decent amount of rain, I don't think high clay content, never noticed ground cracking and this summer was SO dry. I've never paid attention to the stucco houses, but I'll check. We have a few interior cracks in the plaster our 1950 house, but I think it's only where new windows were put in.

I'm definitely okay with having them, but I'm having a hard time picturing how to incorporate them into the style. I am also using this house as inspiration for exterior details (no gutters):

Avalon Bay House · More Info

Here is our exterior as of right now:

Once installed you won't notice them much. If you choose not to install them you will for certain notice standing water around your foundation, and the obvious drip line of the roof.

I'm leaning toward having them most places (not at the front of the porch). But I'm thinking that perhaps the half round would be a better look? Any input on those? Something like this...

Traditional Family Beach Home, Ocean City, NJ · More Info

Any roof overhang that is over an entrance, I think you'll want to redirect the water. My house doesn't have gutters (prior owners didn't finish gutter installations) over three doors used A LOT, and it's awful when it rains. The water just rushes down off the roof and is like a wall of rain, or big drips, you have to get through when ever you leave or go into the house.

I and redoing the exterior and intend to put gutters up there!

Hard rains and the run off from the roof hits the half round shape...and...the water follows the round shape and cascades up and out! Drizzle and no problem! The photo above shows a very large valley which will channel run off in a hard rain right over the gutters. A large diverter may (or may not) help keep the water in the gutter!

I lived in Maine for 10 years - no gutters there due to ice dams. BUT...the soil is very sandy and at least a 3 ft wide bed of gravel is typically placed from the foundation out. There was no problem with rain, either.

Now I live in KY with heavy clay soil. Good gutters and downspouts and good gutter guards (3 big oak trees in small yard) are an absolute necessity.

I'd do a LOT of driving around and seeing what most people have. North of Boston IS New England but it's not Maine (although winter of 2014-15 felt that way, I'm sure!).

Thank you for all of the thoughtful responses! I do hear you on the capacity, and potential splashing on the half-rounds. I touched base with my architect, and he thinks that the K-style will be the simplest solution, and will look fine with the style. Probably best to go with that, being most effective financially and functionally.

Good point about gutters over the entrance tibbrix. I'm thinking, though, that on our design, the front porch may not be a major issue...we will use the stairs on the right end of the porch to access the front door (on the rare occasion that we don't use the side door). We will have a gutter over the side door. Also, the front porch will only have the rain landing on the 7ft depth of that roof, because the large gable above should divert everything from the main roof to the ends of the porch. Is that a reasonable assumption?

Gutters don't cause ice dams but they do complicate the problem. The way to reduce the chance of ice dams is to prevent snow from melting on your roof. One way to do that is to keep the roof surface cold. Two ways to do that are massive amounts of insulation or a ventilation space below the surface of the roof or both. Another way is to allow the heat from the house to reach the end of the eave overhang. All of these ideas work better in the dry climate of the west.

In any event, in New England, the roofing underlayment should be an uninterrupted layer of Grace Ice & Water Shield over the entire roof.

If you do install gutters, the outer lip should be below the extended line of the roof surface. For a steep roof this requires a tall facia board.