If you go by what the Google people say, of course you should use their technologically advanced Automated Bidding Strategies! Why not take advantage of all that machine learning, and focus your time savings on other tasks. But not so fast! There's also that saying you've heard a billion times: "When something seems to good to be true, it usually is..."
Adwords Automated Bidding is SO Expensive
If 1) you can run a campaign by adjusting bids manually (which means you have some experience with Adwords) and 2) if you also have time to run the campaign, the answer is a no brainer. You should use the manual bidding strategy. There are a couple of reasons for this. First, in my experience clicks and conversions using automated bid strategies are always more expensive than if you are manually controlling the click cost. So, for instance, if I set a campaign bid strategy to Maximize Clicks, I can be sure I will get less clicks within my budget than when I ran it manually, because cost per click will increase. This doesn't make a lot of sense. The bid strategy should be called Minimize Clicks. Google is greedy, and if you just hand them your credit card, they are going to max it out.
You Have Less Control. Google Has More
Not all keywords have the same value to a business. For instance you can have one keyword that really captures a user's commercial intent, and another that sort of does. You can have a keyword you really want to nail on position one, and another where position 2 or 3 is fine. How can you impress Adwords with your preference? You can't. Unless you are able to break keyword values into separate campaigns, Adwords is too dumb to take individual keyword value into account. The exception to this is if you are running Target CPA (cost per acquisition) or Target ROAS (return on ad spend) where you can set different values per Adgroup. You can't adjust it down to the keyword level though.
Professional Adwords Management Services Make Sense
Finally, the reason budget matters in the equation, is that if you don't have time to manually run the campaign effectively, and you have a significant budget, it makes sense to hire an agency to run it for you rather than throwing the campaign on autopilot and giving Google your wallet. The money you save in click cost will greatly outweigh the money you spend on an agency in most cases. Don't be fooled though. Large agencies that want to scale can do so by using automated bidding strategies themselves. It's worth it to them because they can run more campaigns with less staff, and you are the one paying the higher cost per click than needed, probably without knowing it.
Above all, if you are new to Adwords, take it slow. Don't think you can learn on the fly, because by the time you are up to speed you will probably have killed your campaign quality score, and be paying through the nose for clicks if your ads will show at all. Automated bid strategies will not save you, they'll just sink you faster.