Knives and slicers each have their place. Seldom do they overlap.
For jerky slices, a slicer is the way to go. You can rely on the butch/clerk at the store or buy your own slicer. With the store sliced, you are subject to the person slicing it's interpretation of how thick you want it. I know plenty that can't read a tape measure ( not that they have one available) and have no concept how thick 1/8, 3/16 or 1/4 inch are or how they relate to each other. You are at their mercy. SLicers are generally marked with reference numbers for thickness, but these numbers don't seem to have any correlation to real numbers ( inch or metric) and they differ by brand slicer. So you tell the guy to slice it on a 15 setting and his slicer only goes to 10...... Or you say a 4 setting and it's paper thin after the last store came up to 3/16 inch.
So.. if you go the store sliced route, go to the same store each time and ask what the setting was when it's the way you want. That way you should get the same result each time.
I have never used a home grade slicer. I have commercial ones at work and lucked into a commercial one for home many years ago. But I see no reason even a cheap home grade unit wouldn't give consistent results. There will be a learning curve.
Add to this that the longer you have a slicer around, the more uses you will find for it. Lunchmeats, summersausage, holiday hams ect.
If you can swing it get a used commercial unit and find a home for it (they are heavy) and make sure it comes with the sharpener. You'll never lose money on it.
A cheap home unit will be CHEAP in almost every aspect. Great for a fill gap til you can do better, but this really is a case of you get what you pay for and buy once, cry once.