Last year, I flew with Delta Air Lines across four continents on 66 flights.During that time, I traveled in all four of Delta's cabin categories, ranging from an economy seat on a 15-hour flight from Africa to lie-flat seats in Delta One from Europe to the US. As a frequent traveler, I typically book with Delta to maximize reward points and maintain my Platinum Medallion loyalty status. I usually choose the most affordable fares and often put my credit-card points toward my flights.Occasionally, I receive complimentary upgrades with my status, but I'll also splurge on a premium seat if the price is right. However, the cost of a premium seat doesn't always align with my expectations. There are a few reasons I'd choose the affordability and practicality of economy seats over the high price tag of premium class any day. I upgraded to Delta One on a return flight from Germany but wasn't completely sold. Delta One was very nice, but I wasn't as impressed as I thought I'd be. Allie Hubers Last spring, I flew to Germany to reunite with my husband after his military deployment. We splurged on an upgrade to the most premium class available for our flight home, spending an extra $699 each for Delta One.The lie-flat seat was a luxury on our 10-hour flight, and the service was fantastic, but our plane seemed a bit outdated and worn. From the clunky entertainment system to the lack of privacy between seats, I felt our nearly-20-year-old aircraft showed its age.We got elevated meals, amenity kits, and complimentary alcohol, but I expected more features or perks considering a Delta One upgrade often costs thousands of dollars.Although our experience fell short of my expectations, I still think the upgrade was worth paying for to celebrate such a special occasion.In the future, I would only justify the cost of Delta One if I knew I'd be on a newer plane with more state-of-the-art amenities. After all, some newer Delta One classes have suites with doors. On one upgrade to Delta's Premium Select class, I got stuck in a middle seat. Delta offers Premium Select seats as a more affordable way to enhance a flight. Allie Hubers When returning from Europe last winter, my husband and I upgraded to Premium Select seats for $209 each on our nine-hour flight.Premium Select upgrades are primarily offered on long-haul flights and come with early boarding (although my status already gets me into the same boarding group that this would). We enjoyed the added legroom and additional recline of our seats, which made them noticeably more comfortable. The upgraded dining, larger entertainment screens, and in-flight amenity kits also elevated the experience.However, we upgraded at the last minute, so our seat options were limited. Unfortunately, I ended up sandwiched in the middle seat next to a stranger. In hindsight, I wish I'd saved the money and kept my window seat in economy.Being crammed in a middle seat for nine hours took away from the premium experience. Next time, I'd try to upgrade earlier so I could choose a better seat.Overall, Premium Select strikes a solid balance between affordability and comfort with its thoughtful amenities and extra space. However, it's not always available on Delta flights, and I'd likely skip it if I couldn't get a spot next to a window. I've traveled many times in Delta's Comfort Plus — but the extra legroom isn't always worth the added cost for me. Delta's Comfort Plus provided more legroom, but I'd say exit rows are similar and more affordable. Allie Hubers A step above economy, Delta's Comfort Plus provides slightly more legroom and priority boarding. For domestic itineraries, this class also receives alcoholic drinks and a better selection of snacks.With my status, I've received many complimentary upgrades to Comfort Plus.Last fall, I flew in Comfort Plus from Seoul to Atlanta after one such free upgrade. As a tall woman, the extra legroom was an added bonus, especially on a 13-hour flight. However, I've found you can get about the same amount of legroom in an economy exit row for a more affordable price.I'm happy to accept a free upgrade to Comfort Plus, but I wouldn't pay extra for these seats, which I've seen cost $100 or more than economy. And, on international routes, Comfort Plus receives many of the same in-flight amenities as the rest of the main cabin. That said, Comfort Plus does get reserved overhead bin space, which is always nice on a fully booked flight. Plus, going on cheaper flights means I can take more of them. I'd be open to flying in upgraded seats if I can get them for a decent price or if there's a special occasion. Allie Hubers Overall, I'd rather book a cheaper flight so I can spend money elsewhere on my trip. A flight is just one of the many costs of a vacation. I also need to pay for accommodations, additional transportation, meals, and activities.By booking affordable economy flights, I have more money to travel more often — and that's always my goal. Plus, I can almost always secure my beloved window seat if I book my trip far enough in advance.However, I'm definitely still open to enjoying the occasional upgrade if the price, plane, and time feel right.