Your inquiry is basically unanswerable without more information. Colombia is at least three times bigger in population with almost 48 million versus Ecuador's 16 million. It is also much bigger in area, almost 4 times as big as Ecuador.
The "best" area - it depends. Do you like big city life, small city life, village life, or rural life?
Do you like the coast with ocean access, or mountains? What climate are you looking for, hot or cooler, dry or not-so-dry?
Are you comfortable speaking only Spanish with very little English language? Depending on where you go in Colombia you may find even fewer people who speak English than in Ecuador.
Although I spent several years as a child in Ecuador, I (currently) like Colombia more not in small part because most of my wife's family lives in Cali and I have been charmed not only by the family's openess and acceptance but also by that of the general population I have met, and the more cosmopolitan aspects of Colombia mixed with the many varied climates and the overall friendliness of the people. My impression is that Ecuador is still a bit behind in modernity and infrastructure although in the big cities there's not much difference.
Bogotá is big, over 7 million, and due to the altitude is cool - and people also say the people are cool, if not cold. It's a big city and has many problems but some love it. It's probably the most cosmopolitan city in Colombia.
Medellín has a great climate and some say it is perfect in that respect, and among the most advanced cities in Colombia, it's the second largest, and many expats would say it is the most cosmopolitan and modern.
Santiago de Cali is the third largest city, hot, both in climate and ambience, the city of salsa, and "sucursal del cielo" with very friendly people but lots of crime although with care that can be avoided - crime is everywhere in Colombia but everyone's experience can be different depending on how you conduct yourself and yes, just also due to chance. Ecuador probably is a bit safer but as I'm sure you know, there are always those who will prey on those perceived as "rich" and that's most foreigners.
And then there are the numerous smaller cities in Colombia each with their own atmosphere and weather and good and bad points - away from the larger cities things are cheaper and life is generally more laid back, with usually less crime and often with incredible vistas of mountains, but often with less amenities readily available.
Colombia has a more well-developed infrastructure of roads and transportation than Ecuador and it's easier to move about from place to place. Plus with the US dollar now around 3000 Colombian pesos (and fluctuating up and down) your money goes a long way. Certainly one can have an equivalent lifestyle in Colombia for less than half of what it would cost in the US and a bit cheaper than in Ecuador (your mileage may vary). The economy in Colombia is strong and is not tied as much to oil as in some other countries, and for now they believe in a mostly free market which means fewer government price controls which means fewer shortages of consumer goods.
Colombia continues to be plagued with the guerillas of FARC and ELN in too many areas but peace talks are in motion. In more rural areas this may be a consideration but in the bigger cities it is not.
Because of "income inequality" and the prevalence of crime, it is advisable not to "dar papaya" and show your wealth in public - nevertheless 99.99% of the Colombian people are hard-working and honest, and although life is not easy for many of them they are happy and well-adjusted in their outlook on life. There is a government-set minimum salary in Colombia just as there is in Ecuador, and it's 689,454 pesos/month or just short of $236 USD per month at the current rate. But only about 50% or so of the population is covered by that in "trabajo formal" - the rest are employed in "trabajo informal" meaning they get along as best they can by whatever work they can find. And even "trabajo formal" is often just contract work for only periods of several months not subject to any automatic renewal.
You must also take into account that Colombia is debating the details of another "reforma tributaria" because the government's spending plans are too ambitious for the current "take" from their citizens and foreigners. If you spend 183 days or more in any 365 day period in Colombia you will be considered a Colombia resident for tax purposes and they will arrogate to themselves the right to tax you on your world-wide income. The US and Colombia do not currently have any tax treaty in place to avoid double taxation but they already do have information sharing agreements in place so they will know what Colombian citizens earn in the US, and what US citizens in Colombia earn in the US, and they will tax them accordingly and at higher rates than in the US. But you should consult a tax specialist in Colombia to make sure you get the latest information.
Hopefully others now in Colombia will chip in and give you more info - but you need to be more specific about what you are looking for, so they can give you specific and up-to-date information.