Venus and Serena Williams will play for the 30th time on Friday night, in the 20th year of their reluctant, unprecedented on-court sibling rivalry. Thirty and 20 are two nice, round, appropriately celebratory numbers; the only number associated with this match that isn’t so nice is three: That’s the round they’ve been forced to face each other in.

Whenever their matches happen, Venus vs. Serena is both amazing to think about—how did one family produce two all-time champions?—and difficult to watch. Every shot they hit at each other seems to be hit with a silent apology.

So what’s the best way to watch the 30th edition of this unique sporting phenomenon? Here are five options to consider.

Root for Venus
At 38, after 20 years on tour, Venus hasn’t shown any signs of slowing down or tiring of the tennis-pro life. She’s even had a resurgence over the last 15 months, reaching the semis or better at three majors. Yet she hasn’t won a big one, or beaten her sister at a big one, since 2008. A victory tonight would be a fitting reward for her lifetime of service and excellence. It would also put her one step closer to winning her first Open in 17 years.

Root for Serena
While Venus is the underdog and perhaps the sympathetic sister for many, Serena has endured her own struggles over the last year and a half. You might say she’s embarking on a third career: First there was the brash youth who won a Serena Slam in 2004; then there was the mature, dominant champion who did it again in 2015; now she’s trying to win her seventh Open, and her first since 2014, as a new mom, a quest that has made her more culturally influential and popular than ever. If she wins this match, she’ll also be one step closer to catching, and then passing, Margaret Court for the all-time Grand Slam title mark. That’s a record Serena really should own outright, isn’t it?

Root for a Good Match
Williams sisters' matches have been understandably uneven, and few have risen to the status of classics; it’s difficult for either of them to compete with abandon against each other. Two exceptions to that rule have come in US Open quarterfinals, first in 2008 and again in 2015. Both times, Venus pushed hard, but that only inspired Serena to overcome her competitive reluctance and push back harder. When they bring all of their speed and power to bear on each other, the result is predictably spectacular.

Appreciate their unique skills
Speaking of their speed and power, you can also focus on that, rather than picking a side. It may be hard to remember now, but Venus and Serena were a big part of the sport’s 21st-century evolution: Their serves were the most dominant in WTA history, their open-stance backhands broke the technique rules of the time, and their relentless attack from the baseline set a new standard that the rest of the women’s tour is still trying to match. Here’s a chance to see the two standard bearers together on one court.

Appreciate their presences
This era of tennis has produced more than its share of players who will be talked about a century from now: Roger Federer, Rafael Nadal, and Novak Djokovic may be the three best male players in history, and they’ve all played in the same 20-year period. That goes double, literally, for Venus and Serena. Not only are they two of the game’s great players—imagine how many major titles Venus could have won if it weren’t for Serena—they’re also two of its pioneers. They changed how the game looked and how it was played, and now they’re changing how long we think a champion can remain a champion. The Williamses have been around for so long that we have trouble imagining the sport without them, but they’ll have to stop someday. U.S. tennis fans especially: Don’t take our two greatest players for granted tonight. You’ll want to tell your grandkids that you got to see the Williams sisters.