If you were to do a survey of people who shop for groceries on a regular basis and ask them which stores have the best customer service, competitive prices, and fun mix of products, they’d probably give you two answers – Costco and Trader Joe’s.

Of course, Costco and Trader Joe’s clearly have very different business models.

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Costco is a membership-based store that’s able to offer consumers discounts by selling products in bulk.

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Trader Joe’s, on the other hand, does not require any sort of membership.

In fact, Trader Joe’s doesn’t even make shoppers sign up for a rewards card to snag discounts. Instead, it makes its everyday low prices available to anyone who sets foot in the store.

Costco and Trader Joe’s are also similar in that both have generous return policies. At Costco, you can bring back pretty much any item at any time, no matter the reason.

At Trader Joe’s, you’ll generally enjoy a hassle-free refund, too, especially if there’s a quality issue with the item you’re returning.

Costco and Trader Joe’s have major drawback in common

Image source: Brooks Kraft LLC/Corbis via Getty Images

Shopping at Costco and Trader Joe’s isn’t always smooth sailing

While there are plenty of benefits to shopping at Costco and Trader Joe’s, one thing people often complain about is having to battle crowds.

Because both stores are so popular, they tend to be pretty busy – especially on weekends and in high-profile locations.

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If you’ve ever set foot in a Costco on a Saturday or Sunday, you may have found yourself cursing under your breath (or out loud) in the parking lot due to your inability to get a spot.

And if you’ve ever been to a Trader Joe’s location in a big city, you’re probably no stranger to wraparound lines at the checkout area (sometimes so intense that you’re practically stuck waiting outside to pay for your haul).

Thankfully, Trader Joe’s tends to do a good job of managing crowds by having store employees scan groceries quickly and move people through the queue efficiently.

Costco recently said that it’s working on a more efficient checkout process for customers, and that it’s toying with options that could include “scan and go” technology.

Costco and Trader Joe’s share a key practice consumers don’t like

Even though crowds at Costco and Trader Joe’s are a pain to deal with, they’re a testament to how awesome both retailers are. Still, there’s one practice that both Costco and Trader Joe’s employ that customers do not love at all – discontinuing products on a regular basis.

Costco and Trader Joe’s pride themselves on keeping their inventory fresh. But both stores are only willing to stock a limited number of products at the same time.

Related: Costco members angry over very personal product change

For new products to come in, old ones have to sometimes get phased out. But what inevitably happens is that at either store, you might fall in love with a certain product only to never see it again.

Costco recently eliminated popular products such as its Kirkland Signature soy milk and Sweet Heat snack mix. In both cases, fans were saddened to see these beloved items quietly get pulled from shelves.

Meanwhile, there are many Trader Joe’s products whose absence hasn’t gone unnoticed.

The company did away with a number of granola bar types in recent years, including Chocolate Chip Brownie & Oat and Vanilla Almond. To this day, there are probably lost parents wondering what snack to replace them with to keep their kids happy.

Fans of Trader Joe’s also miss the Thai shrimp gyoza and gorgonzola crackers, among many others.

More retail:

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The reality is that Costco and Trader Joe’s don’t just yank products at random. They make those decisions based on how well a given product is selling.

But it can still be a huge blow to see a staple item on your weekly shopping list suddenly disappear from the shelves without warning. So once you find that product you just can’t live without, it could pay to stock up.

Maurie Backman owns shares of Costco.

Related: Trader Joe’s makes a customer service decision Costco won’t