Mormonism is sometimes referred to as a "book and bosom faith" because of its heavy reliance on a heartfelt feeling regarding its most precious book. Since 1830, Mormons and new converts have been encouraged to "pray to know that the Book of Mormon is true". Anyone who asks with a sincere heart is supposed to receive confirmation from the Holy Spirit, called their "testimony". Of course, anyone who doesn't receive this testimony is said to have not had a sincere heart when they prayed.
This test is not unfounded. It's not something that doesn't flow naturally from the Mormon scriptures. Rather, this test comes from the Book of Mormon itself, from Moroni 10:4-5. But while this test comes from the Mormon scriptures, it is completely antithetical to the Christian scriptures. Christianity is not a book and bosom faith, but a highly intellectual one. Rather than being told to pray and hope our highly deceitful heart (Jeremiah 17:9) won't lead us astray, the Bible tells us to test all things (1 Thessalonians 5:21).
In Acts 17, Paul and Silas preach in the synagogues at Berea. Their message was not one of intellectual laziness. Rather, when Paul and Silas preached, the Berean Jews searched the scriptures to see if Paul was preaching the truth. The result wasn't that they were told they were insincere, but rather, they were commended for their diligence (which, of course, ties in perfectly with 2 Timothy 2:15).
But another thing you'll notice is that the Bereans weren't the only ones who believed. Honourable Greeks also believed. This is no small thing. Greeks are well known for their extreme scepticism. Many of the arguments used by modern sceptics come from Greek philosophers. Put simply, if you convince many prominent Greeks, you have a pretty strong, evidence based philosophy.
And of course, that's exactly what the Bible is! Evidence based. The scriptures the Bereans searched so diligently were not pulled from thin air. Nor were they written in a non-existent language on some mythical golden plates. Rather, they were written by eyewitnesses, sometimes even to eyewitnesses, and verified by miracles. No book is more historically or geographically accurate than the Bible. Even what little science is mentioned in it was ahead of its own time, some of its insights being verified as late as the 1900s. If you want to prove the Bible, you are actually in a better position today than anyone in history has ever been, having access not only to all the evidence gathered throughout history, but also to several highly developed search engines to find it with, allowing even the layman to outsmart a scholar.
The same cannot be said for the Book of Mormon, a book so "correct", it has been changed several times since Smith originally published it. Its geography is appalling. Its history is atrocious. Its science is abysmal (and in some cases, outright racist). Newer developments are not rescuing it, but serve to further condemn it. All of this before we have even picked up a Bible. If the Mormon God really did exist, he went senile before he said "let there be light".
Ironically, Moroni 10:4 pokes another hole in Mormon theology. Notice how it calls God the eternal father. Does modern Mormonism teach an eternal God? One who lives from everlasting to everlasting (Psalm 103:17)? Not hardly. Their "God" was once a man, and has now achieved divinity through obedience to his own god. In other words, if you look at the very text they use to convince you to pray about whether Mormonism is true, you should instantly be able to tell that it's not.
An honest test is always more valuable than an honest prayer. Prayer is, of course, rather important, but intellectual investigation is both commanded and commended in the Bible. Just as I do not need to ask God if it's ok to steal a car, but rather I can find His judgement on theft in the scriptures, so also is scripture 100% sufficient for judging other religions (2 Timothy 3:16-17).