It sounds like your biggest issue is that you don't want to have to pay for unexpected repairs over the life of a car that you are hoping to keep for a long time. If you're planning on keeping a car for 10+ years it's going to need some work done at some time, hopefully not a full engine swap but something will likely happen. Plus you'll need to plan for paying for all the high-mileage preventative items anyway at some point such as CV boots, timing belt, etc(easily in the 1k-2k range depending on car). If you want to keep the car long term and not have to worry about having savings for unexpected repairs you could purchase an extended warranty up front and get bumper to bumper coverage for 10yr/100,000 miles.

Also, if you're only spending 20k up front, that level of car is not going to have much resale value left after 10 years (if you drive the average 10-15k miles a year) so I wouldn't let resale value factor too much into this.

Having owned multiple 100,000+ miler cars myself I can tell you that they don't all age gracefully. If you're planning on keeping a car that long make sure that you consider whether you're still going to want to drive that car many years down the road. Things that make a difference in this aspect are items such as ride comfort, interior construction quality, convenience features... I've driven many mazdas as rentals as well as my buddy's high-mileage Mazda and I personally wouldn't want to keep a Mazda that long. I just bought another "long term" car and ended up with a 2011 Volvo S80 with less than 40k on the odometer for 17k. It has a very reliable power-train and is the most comfortable car I've ever been in. Plus it uses a timing chain and not a belt so there's a $1.5k savings down the road for not having to change the belt. Food for thought.