Amazon Prime Day vs. Walmart: How to Know Who Has Better Deals

— -- Amazon Prime Day deals, which the company touts will outnumber those it offers on Black Friday, may cause frustration for people who aren't glued in front of their computers today.

Analysts and retail experts have mixed reviews about Amazon's deals and those of its competitor Walmart, which launched a sale in response.

Amazon's one-day shopping event which launched at midnight PT overnight is a new promotion for Amazon Prime customers, who pay $99 a year for perks like free two-day shipping and streamed entertainment content. Students pay $49 a year. The company said it will have "thousands of lightning deals," with new ones as often as every 10 minutes, and seven "deals of the day."

Walmart launched a rival sale today including more than 2,000 online exclusive "rollbacks." The discounted items will last 90 days and will include electronics, home, baby and toys. The company will also decrease its free shipping minimum order to $35 from $50.

One advantage that Walmart is pushing heavily is that it indeed a brick-and-mortar store with often faster availability.

“Again, an advantage the brick-and-mortar retailers have is same-day availability via buy-online/pick-up in-store, which Walmart is trumpeting very loudly on its website," noted Charles O'Shea, Moody's vice president.

Amazon advertised a variety of Kindles at "rock-bottom prices," O'Shea said, "potentially to entice Prime members to enter its content ecosystem."

One popular configuration was a black Fire HD 7 tablet was $114, or $60 off, that sold out, with more than 17 hours until the end of the promotion. O'Shea said it's difficult to assess via the website how many of each product were originally available.

"I was surprised how quickly some of the lightning deals were 100 percent claimed," Kyle James, founder of Rather-Be-Shopping.com, told ABC News, adding that these were "things that were a decent deal at best."

Here are some of the deals that James thought were the best so far:

1. $60 off the Fire Kindle HD 7 (sold out)

2. Sony 16GB flash drive for $6.99, 59 percent off

3. HP Stream 7 32GB Windows 8.1 Tablet for $59.99, 40 percent off

4. VTech Sit-to-Stand Learning Walker for $20.99, reg. $34

"Amazon did a great job building buzz around the event and it seems to be paying off," James said. "The website is definitely slower than usual, which tells me shoppers are responding. And for the first time ever I actually couldn’t get a page to load; hit refresh and it finally did load.

"I like how Amazon is letting shoppers know what deals are forthcoming. They seem to be holding back a lot of their big electronic deals on HDTVs and laptops until later in the day. Let the buzz build around the water cooler, then release them when they have a captive audience."

Here are some of Amazon's best deals, according to Coupons.com general manager of e-commerce Helen Fang:

1. Rosetta Stone Spanish (Latin America) — Level 1-3 Set for $159.00 (60 percent off). Fang expects more languages to come throughout the day.

2. Sanuk Women’s Yoga Mat Wedge Flip Flop for $12, 79 percent off

3. Amazon Elements Baby Wipes, Unscented, Flip-Top, 80 Count (Pack of 6) for $4.40, 60 percent off, Save & Subscribe: $4.18

4. Kindle, 6-inch Glare-Free Touchscreen Display, Wi-Fi — includes special offers - for $49, 38 percent off

5. Fire HD 7, 7-inch HD Display, Wi-Fi, 8 GB — includes special offers, white for $79, 43 percent off

8. Amazon Fire TV Stick. "While we saw this on Black Friday for $24.99, this is the cheapest price it’s been at $24," Fang said.

A spokesman for Walmart said the response of customers to that sale was "incredibly strong."

"It seems like the word is spreading fast. Our customers know that every day is a great day to save at Walmart and they are flocking to our site for the thousands of rollbacks we offer," said Walmart spokesman Ravi Jariwala. Some of Walmart's top-selling items today include the iPad Mini 2 for $265, for savings of $164 savings from the retail price and the RCA 55-inch TV for under $400.

Here are some of Walmart's standout deals, according to Fang:

1. Sceptre 50-inch 1080p LED HDTV for $349, marked down from $499.99

2. RCA TV for $399.99, marked down from $799.99

3. Realtree 10-feet by 10-feet Slant Leg Canopy for $49, from $99.99

4. Shark Easy Spray Steam Mop DLX for $20, from $49.99

5. Flexible Flyer Play Park swing set for $159, from $249.99

6. Apple iPad mini 2 16GB Wi-Fi + AT&T: $365, from $429

"Walmart is quite unimpressive," James said. "The best deals are on stuff they’d be clearing out anyways: patio furniture, BBQs and swimming pools."

James said the following are "good" Walmart deals:

1. Black and Decker Drill and 133-piece Home Project Kit for $50, allowing customers to save $30. Amazon sold something very similar for about $95.

2. Toshiba 15.6-inch Satellite Laptop for $377, for a savings of $253, which James called "attractive." It has an Intel Core i5-4210U processor, 8 GB memory and 750 GB hard drive.

3. Sceptre 4K 49-inch HDTV for $429.99, discounted $470. James said it is "off-brand but a good deal."

Here are some of the other deals Walmart is touting as some of their best:

1. Disney's Frozen Anna Doll for $10 (customers save $15)

2. Coleman 12-Person Tent for $265 (customers save $164)

3. Intex Above Ground Swimming Pool for $199 (customers save $200)

4. Urbini Sweetli 4-in-1 Convertible Crib for $129.98 (customers save $70, Walmart.com exclusive)

5. Upper Bounce Classic Trampoline with Safety Enclosure for $201.46 (customers save $27.54)

6. Hello Kitty Girls' Popover Dress for $7 (customers save nearly $6)

7. 9 by Novogratz Bath Accessories Set for $19.99 (customers save nearly $10, Walmart.com exclusive)

Amazon Prime Day ends tonight at 11:59 p.m. PT. Anyone can see Prime Day deals on Amazon.com, but to purchase the deals, you need to be an Amazon Prime member. Amazon Prime members can share the two-day shipping benefit with up to four household members. Customers who purchase a Prime membership for a small business can invite up to four co-workers to shop with that corporate account.

Non-members can decide to become members anytime on or before July 15, but a spokeswoman told ABC News she suggests they join before the deals start so that they don’t miss out on something they really want while signing up for a membership. New members can sign up for a free Amazon Prime 30-day free trial with a credit card, but beware your credit card will be charged the full fee if you don't cancel your membership before it ends.