People don't like to say it because they're afraid of sounding lazy, but you should do whichever is easier. Is building one of them going to be easier than the other? Is marketing/selling one of them going to be easier? Does one of the ideas require raising money?
Building a sustainable business is hard enough in and of itself. If you can avoid having to woo investors, or dealing with Chinese factories, or months long sales cycles, do it.
In addition, this will force you to think realistically about the skills and deficiencies on your founding team.
There's a natural tradeoff here though: the easier a business is for you to build, the easier it is for others to copy it. If you're a skilled practitioner doing something near the limits of your abilities, it in no way guarantees that you'll find product-market fit, but when you do, the market is more likely to be yours for awhile. There will be fewer people out there who are capable of competing with you and it will take them longer to get up and running.
Agreed. If something is too easy it gets too competitive and you're working for scraps. But if one is a skilled practitioner, pushing the limits of that skill will be "easier" than learning a completely tangential skill.
Easy also means that people are less willing to pay high prices for the company. But sometimes it's safer because you're not competing with people like Rocket Internet, who can hire a thousand people overnight capable of working 12 hours/day on some idea.
Building a sustainable business is hard enough in and of itself. If you can avoid having to woo investors, or dealing with Chinese factories, or months long sales cycles, do it.
In addition, this will force you to think realistically about the skills and deficiencies on your founding team.