Much of the "Should I get this detector?" or "Should I get that one?" is moot, really. SO many variables go into the usage that it is impossible to say one is better than another.
What is constant is that good makers put their machines through the paces to ensure that YOU will get a product that meets your needs, the vast majority of the time. In fact, it behooves you to have more than one. I recently discovered a site/detector combination that allows me to get great results, when another instrument in the same location wouldnt do as well.
With that being said, can you indeed learn for certain if a BH LS is better than a Garrett Ace 250 from a few questions and a hodgepodge of answers. The answer is simple: NO!
Each is a different machine, wth different features, which will ultimately be used by YOU in the way you see fit. I can say that the Ace 250 is a good little machine. It is easy to use, has plenty of good features, surprising depth and a good price. The after-sale service is also top-notch, should it ever be needed. Charles Garrett, said that his goal was to make a detector with all the features of a high end machine, yet packed into a $200 package. He succeeded.**
Some will say the similar things about the BH LS. BH has come a long way in recent years in terms of product performance and market presence - I even hear that their service is improving! While to me, they remain a somewhat anonymous, even questionable company, the recent merger with Fisher and the consumer drive for ever better equipment may change all that.
But, you cannot possibly know from my comments, or those of others, that either will suit you.
** (I personally wouldn't expend the effort to get the "Pro" package for the Ace 250... Id rather have the sniper for the Ace.)
Here's what I usually do. Maybe this one suggestion will actually help.
Get one or the other USED and see what develops. If you dont like it, sell it and get the other. If you don't like either, you will not have given away much money in depreciation (The Ace holds its value well, due to it's overall abilities and demand. The BH not so much, but it has a devoted following of users).
The other possibilty is that you will like both, probably for different reasons. If you are lucky enough for that to happen, you will not have spent near the money you might have new and can likely feel better about owning BOTH, this way.