By reading an online arts magazine you are opening yourself up to even more culture than you could have hoped for when attending a museum. Obviously, there are some cases where this will never be true, but flying to Paris to see The Louvre is much more expensive then getting an online magazine subscription.
One of the only major drawbacks to looking at art online is that sometimes the texture of the piece is lost. Sometimes, seeing the brushstrokes of a painting are part of what can make it so beautiful and moving and looking at a painting online can definitely mute that beauty slightly. There are other less obvious reasons but they are more specific and happen less often. When you are looking at an online art magazine, if there is a larger piece sometimes seeing that piece in person can affect the viewer much differently than by just looking at it on a screen.
By looking at an online arts magazine readers are able to find out a lot about new artists. You can read a bio about the artist you are currently looking at and even comment on the interview. The people running the magazine might present the comments to the artist, if they so choose, and you might end up getting a chance to speak with the artist! It sounds far fetched but you have a better chance going that route than hoping that Pablo Picasso will rise from the dead to have a beer with you. Maybe if you think hard enough Andy Warhol will check out the online arts magazine with you, though.
If you like looking online free art is always available to check out. Posting free online art is a great way for artists to get the word out about their work. If they submitted to an online arts magazine they might be able to get sponsors from other art related businesses and maybe even start selling their work.
Subscribing to an online arts magazine will broaden your mind and your tastes in a positive way.