I use 3 3/4" Lightolier whenever possilbe

A lot depends on type of lamp and wattage, plus whether the fixture is a downlight, wall washer or adjustable. Lots of choices! Good luck!

It seems to me that the purpose of recessed lighting is to make the source of the light less noticeable and to put focused light on task areas and accent other objects and surfaces. Therefore, smaller is generally better but I rarely use 3" fixtures. Any reduction in light output can usually be corrected by placing the fixtures closer together and/or using low voltage fixtures. Of course, more fixtures increases the cost but good lighting is rarely a bargain.

Whatever size you choose it is a good idea to avoid Reflector (R) lamps because they don't last very long and are more visible with more glare than PAR lamps especially if the PAR lamps are frosted.

The smaller fixtures are also well suited for the new LED lamps which use much less energy and last much longer than fluorescent lamps and provide more and better light. I replaced all of my recessed lamps last year and the breakeven was in about 6 months and the lamps continue to drop in price.

Reno, what lamps do you use in your fixtures for general illumination? Are they low voltage or LED?

Lightolier are very high quality fixtures. If it were my own house, I'd probably use Halo unless there was a specific setting (wall wash, adjustable, etc.) for which only Lightolier had what was needed. Prescolite is another less expensive option, if they have the function and trim that is desired.

In general I don't believe much in general illumination from recessed lights. I don't like to light the tops of people's heads and open floor spaces unless there is a really nice rug centered in a space. I light the task surfaces and walls and then see if any large area needs additional light which is rarely the case. However, I have put 3 3/4" fixtures in a 4 ft x 4 ft grid over an entire large living room ceiling for clients who didn't like shadows.

I use Lightolier unless I am forced to use a Juno fixture for some rare reason. I just can't understand the Halo catalog and rationalize the additional cost by the savings in design time. Laziness is probably a factor too but everyone is usually happy with the fixtures. People remember poor performance instead of cost.

I put Halo in my house 30 years ago and the trim rings are now different shades of yellow and one is missing from a stray hockey stick but I probably saved $75 at the time and was able to buy some used tires for my Campmobile.

invest in insulation contact air tight recessed lights.
not just IC but ICAT
the icat lights are not much more per case,
but to retrofit an ic light to air tight
is about $15 per light.

recessed lights leak air from attic into the house.
as insulation is next to these lights, the particles
from insulation also enter the house.

make sure that can has no holes in housing,
stickers inside cans are confusing. most say
air tight in large writing & when used with the
following trim kits..in smaller writing.

I'm not much help with sizing..partly because
I deal with the problems of IC recessed lights
all the time. just not crazy about the product,
but my personal bias.

best of luck.

I agree with ER. Cans are leak, and have very pour light spread. I like to avoid using them on my projects. There are plenty of ways to light spaces without using recessed cans, and also not using ugly surface mount dome lights too. especially in kitchens. horrible task light source, that is why people need to add so many of them.

Sorry misspelled - Lzerarc

a lot depends on your room sizes and layouts. In a kitchen for example, a good way to light the space is to provide indirect lighting to illuminate the space, and then provide directional task lighting at the source, rather than on the top of your head. Take a typical L shape or U shape kitchen with an island. I like to install T5 linear lights above the upper cabinets installed on a slight angle to direct the light up and out into the kitchen. A continuous row will provide continuous lighting to illuminate the space with indirect lighting. With indirect lighting, you do not have shadowing. I then put a continuous strip of LED lighting under the cabinets at the furthest outer edge (away from the wall). This allows task lighting directly at the source; your hands and what you are working on, not to be shadowed by overhead cabinets, bodies, etc.
Island and bar lighting I like to use hanging pendants, either LED or CFl loaded. Again, this gives source lighting. Over kitchen sinks, similar application.
For general bedroom lighting, this can be done with a ceiling fan light (I personally love ceiling fans and the ability to spread air). But if a ceiling fan isnt your thing, then there are thousands of surface mount or "mini chandelier" style fixtures. Lamping is also another way to spread the light. Outlets can be broken to be switched. Sconce lighting in living rooms can provide dramatic effects and provide nice mood lighting at night.

Can are not so big of an issue when installed in not attic spaces, or an unvented attic (attic that is spray foamed for example).

Thanks this helps a bunch!