I cannot say that one credit monitoring service is "better" or more accurate than another -- and in fact most provide very similar services.
I have tested Lifelock.com, and it seems effective.
I do want you to be aware, however, that I do not think that any credit monitoring service is a great service for consumers, since it is something you can do yourself for free. For an outline of how to monitor your own credit, you should visit: Free Credit Monitoring
You can obtain a free copy of your credit report once a year from each of the three credit bureaus by visiting AnnualCreditReport.com. Once you have obtained a copy of each of your reports, carefully review them for errors, and disputes as necessary with the appropriate bureaus.
Why different companies produce different scores
You mention in your question that there is a significant difference between your Experian and TransUnion credit scores. There are two primary reasons why the same consumer can have different credit scores with each of the three major credit bureaus. The first reason is that the three bureaus use similar, but not identical, formulas for calculating a credit score based on the information in your credit reports. The second is that each of your three credit reports can contain significantly different information about your credit history. With each credit bureau using a different formula to calculating your credit score, and using different data, it is no wonder that the results can differ significantly.
There are several popular credit scoring models used by the credit bureaus, developed as proprietary formulas by various companies. Some of the most popular are CreditXpert, PLUS (developed by Experian), and, the most well known, FICO (developed by Fair Isaac Corp.).
While each of these models looks at the same basic aspects of your credit history, slight variations in how different factors are weighted mean that, even when based on the exact same credit history information, the resulting scores can vary by 50 points or more. The variance caused by scoring models could easily account for the difference between your TransUnion and Experian scores.
In addition to using different scoring models, the three credit bureaus are likely showing different credit history information on your credit reports. It is quite normal for the bureaus to report some different information from one another. I encourage you to carefully review the information on all three of your credit reports to make sure that everything appearing on the reports is accurate. Again, if you find any incorrect or unknown listings, you should dispute them with the credit bureau showing the inaccurate data.
See the Federal Trade Commission document FTC Facts for Consumers: How to Dispute Credit Report Errors for more information.
What credit score will my lender use?
Lenders are aware of the potential problems that can result from differences in the scoring models and information used by the different bureaus, which is why many lenders use your middle credit score. This fact is a good indication that wide variations in credit scores are a common occurrence.
For more information about credit scoring, credit reports, and how they affect you, I encourage you to visit the Bills.com Credit Resources page.
I hope this information helps you Find. Learn & Save.