IMO, either one one would do the job.

Thanks!

Here in San Diego county, I used neither on my sweet potatoes...just heavy layer of tree-chip mulch. They grew well and I got about 30lbs from two plants. I'm planting more this year, as consider them pretty AND foolproof. My sunniest planting areas are in front and side yards, so looks are important.

What if you live in a colder zone? So far my sweet potatoes aren't doing anything, and I wonder if it's hot enough for them. I didn't lay plastic or groundcover down....

Here's what Sandhill Preservation says. They are ones that I got mine from and they are also in got started in Idaho where it was pretty cool and not thought of as sweet potato country:

(Also see the link below)

First: Forget what climate zone you are in. That has nothing to do with growing annuals, that is for over wintering plants. Parts of coastal Alaska are in Zone 7B. here in Iowa we are in Zone 4B. If we set out plants in the garden on the same day in both places it is almost certain the folks in Alaska will not have anywhere near the success we will have here.

Second: Do not set the plants out when it is very cool. They hate cold and just sit there shivering waiting for heat. Do whatever you can to make it warm and toasty for them and they will reward you.

Third: Do not think you need lots of roots on the slips when you plant them to be able to insure success. The more roots the more stress when transplanting and the more they will be stunted. The key when setting out the slips is to have very few roots and keep them as wet as possible in the garden for the first seven to ten days. Then back off on the water and they will go crazy. The worst possible thing you can do upon receipt of the slips is to pot them up and wait a few weeks and then transplant to the garden. You will have lost a good two weeks of positive growth and will have given them two chances to slow down. The more you slow them down, the less yield you have. The more times you transplant them, the more nonuniform roots and the less roots you will get.

Fourth: This is the most important thing when it comes to sweet potatoes. It is the heat units that determines success, not the number of days nor plant zone, but heat units. I have been an avid weather observer for almost forty years and have files of weather data to go with files of planting data. This year, thanks to the help of Natalie, I was able to put the two sets of data together and arrive at some conclusions that I had already suspected, but had never had the time to confirm. It takes about 1,200 heat units for our early varieties to reach a decent crop of usable sized roots. I use the term usable sized as I think, for many a sweet potato, the size of a nice fat bratwurst is about the best size for keeping and for baking. Bigger than that is ok, but they do not sprout as well nor keep as well because they suffer from bruising much easier. The question you must then ask yourself is, "How is 1,200 heat units determined?" I offer the following examples. To get heat units you take the day's high temperature (maximum) and the day's low temperature (minimum) and add them together. Then divide by two and subtract 55 from that. That gives you the heat units.

Example 1. Daytime high (maximum) 75 deg. F, nighttime low (minimum) 45 deg. F. Add those together and divide by 2 you get 120/2 or 60. Subtract 55 and you get 5 heat units. If that is your typical Summer, then you will need 240 frost free days to get a crop. It doesn't take a genius to realize that if you have Summertime days like that, you are probably not going to have 240 frost free days because that is 8 months.

Example 2. Daytime high of 90 deg. F, nighttime low of 70 deg. F. That gives you a heat unit for the day of 25 which is just about perfect for maximum growth. Heat units per day greater than 25 seem to have more of a negative impact because of the massive amount of water lost through transpiration. If you can keep 25 heat units a day, then you only need about 48 days to get some usable roots. This is pushing it a bit as there are some limits to daily plant growth. The best growth I have ever seen here is planting around July 18 and having a decent crop by our first frost of October 2, which is about 76 days. By no means do we have temperatures that are perfect for growth each day here in Iowa, but hopefully this shows some data that can help you determine if you can grow a crop.

Fifth: For those who have read the above information and feel that it is now hopeless for them to try to grow sweet potatoes, I offer the following challenge. You can "alter" your heat units in a cold climate. The only way I was able to grow much the three years I spent in the Panhandle of Northern Idaho, where nighttime temperatures got down to the 30's most nights, was to trick or alter the environment. I used Lodge Pole Pine saplings and made an A-frame structure and covered it with plastic. I then enclosed both ends, only opening the ends on the hottest of days and faithfully closing the ends every night. There, the average daytime high was around 80 deg. F in the Summer and around 40 deg. F at night, in other words about 5 heat units a day for most days. by using the A-frame plastic enclosures, I could get it up to 95 deg. F in there in the daytime and keep it around 55 deg. F at night without any supplemental heat source. Therefore, I could get 20 heat units a day instead of 5. I never had the courage to try sweet potatoes there, but by using this method was successful with melons, tomatoes and cucumbers that otherwise were impossible or close to a miracle. You can speed it up even more with planting on black plastic, something I never had access to at that time. Living here in Iowa there are no Lodge Pole Pines so a similar structure could be made out of stiff #9 wire or, if you are talented, plastic PVC pipe.

Here is a link that might be useful: Sweet Potato grow guide from Sandhill Preservation

I have grown them with black plastic and without with good results both ways. If you need more heat, use black plastic rather than landscaping fabric as the fabric likely will not add heat.

Myself, I prefer a bit of root as then they transplant without stress.