Fantastic review Arbiter.
A few insights Bajara:
Regarding down payment, if you can afford, do 20% down and no additional PMI expenses; if you cannot do 20% down or could do 20% down but will run out of all cash, wise to do 15% down and have PMI for 5%. It will not take very long to pay off the 5% PMI.
Generally accepted standard is, the monthly mortgage should be at or lower than 25% of you monthly pre-tax income.
Ideally speaking, for a family of 4 and on and off visiting guests, 4 bed rooms; an office; plus formal living and everyday living rooms; formal and everyday dinning areas -- but it might be difficult to get all of these in one house. So, might have to do come adjustment/compromising.
Its a personal choice that depends of several factors (like builder, pricing, availability, locality etc.) whether to get a brand new house or fairly new but pre-owned house. If you can find a new house that is within your budget and meets all your requirements/expectations, by all means - new constructions have (usually) newer and latest amenities; newer appliances like air condition, heater, microwave, dishwasher, over/cook-tops, some even have refrigerators. New appliances have warranties and usually last a few years without any minor/major issues if handled with basic care.
Area wise, I think anything around or above 2500 square feet should be adequate for a family of 4. 2 stores will provide more area and space in both levels but like you've listed comes with pros/cons.
Depending on where you live, need to take care of lawn: lawn mow (something you can do by yourself), in the summer, usually 2 times a month. Gardening, planting, yard work, depending on your level of interest -- the more additions/upgrades you add to your yards, the more regular maintenance work will be required. Watering, in the summer time, usually 3 times a week.
Home owner's warranty for appliances: usually they have a charge of around 60$ for visit calls (standard in mid west) for diagnosis and minor fixing, also covers follow-up if needed; if it requires equipment change or replacement, this is not covered under basic home owner's warranty. The basic warranty costs around 500$plus 60$ for technician charge per visit. Even if you do not have warranty, it will cost around the same (or slightly more depending on the job) if you call a well reviewed technician from Angie's list. Hit or miss personal choice.
Hope this provides you with some insights.