FINALLY a topic on this forum about which I have proficiency.
Which test you take depends upon your objective(s). Be advised that the "health traits" advertised are a work in progress. The same can be said for ethnicity estimates. It's still early days, and the estimates change regularly.
If you're into genealogy, then it depends upon where you are. If you're in Europe, then MyHeritage is the most-used one there. If America, then BY MILES Ancestry has the largest database for genealogical matches.
I'm going to gently try and reverse the question on a family serial killer. I *especially* want those found and rooted out. To that end, I have downloaded my raw data from Ancestry, uploaded to GEDmatch, and opted in for police matching, so that any John/Jane Does match, and killers as well. If I can help give a nameless murdered woman her identity back, or help find a murderer, then I will be pleased as punch. I'm not covering anyone's ass for something like that.
I do have one caveat - unexpected parentage is staggeringly common. You possibly have no idea. It's referred to as an "NPE" meaning "Non-Parental Event" or, colloquiallly, "Not the Parent Expected." Your sainted momma is human, too. There are a number of private support groups for these circumstances, and there are people who are absolutely wizardly at working the DNA findings to identify biological parents and relatives. They are called Search Angels and they work for free. I have done this myself, and it's very rewarding to e.g. give an adoptee the knowledge of their tribe.
With any luck, the previous paragraph will be irrelevant to you, but you should know of the resources available if it is.
I'll stop now. I can talk DNA all day long, and get you hopelessly confused. LOL
If you go with Ancestry, their kit is usually on sale on Amazon for about $59 with free shipping. If it isn't, and you can wait, then just watch it for the frequent sale price.