Here is a side-by-side comparison between the two games.

• Campaign Mode?
  • VT9: Yes - World Tour
  • GST: Yes - Grand Slam
• Create-A-Player?
  • VT9: Yes - Home in World Tour
  • GST: Yes - The Locker Room
• Online Play and Local Multiplayer?
  • VT9: Yes
  • GST: Yes
• Can Use Nunchuk?
  • VT9: Yes
  • GST: Yes
• Practice Area
  • VT9: Yes
  • GST: Yes
• Tutorial Games

How are the Tennis Motions Handled?

• Forehand
  • VT9: Wii Motion Plus - EasilyRecognizes Motion
  • GST:Wii Motion Plus -SeldomRecognizes Motion
• Backhand
  • VT9:Wii Motion Plus - Easily Recognizes Motion
  • GST:Wii Motion Plus - Seldom Recognizes Motion
• Lobs
  • VT9:Wii Motion Plus - Easily Recognizes
  • GST: Uses "A" button and any swinging direction of WiiMote - Consistent
• Drop Shot
  • VT9:Wii Motion Plus - Moderately Recognizes Motion
  • GST: Uses "B" button and any waggling of WiiMote -Consistent
• Slice
  • VT9:Wii Motion Plus - Seldom Recognizes Motion
  • GST:Wii Motion Plus - Seldom Recognizes Motion
• Service
  • VT9:Wii Motion Plus - Easily RecognizesMotion
  • GST:Wii Motion Plus - Moderately RecognizesMotion
• Volley / Smash / Net Play
  • VT9: Wii Motion Plus - Easily Recognizes Motion. Raise WiiMote to ready volley
  • GST: Uses "Up" button for Net Play

Other Notes:

In GST, it doesn't account for the wind-up of the racquet before hitting the ball. For example, if you are bringing your WiiMote back to anticipate a forehand or backhand, GST will record it as a swing. In VT9, the player's A.I. goes into wind-up animation to anticipate the hit. This avoids mistaking the wind-up from the actual swing. However, if the person holding the WiiMote anticipates it as a backhand and the screen shows a forehand, well then VT9 just made you look silly. In GST, you can get away from just waggling the controller but not VT9. However, VT9 is sometimes too forgiving.

Detailed Ratings (1-horrible / 10-superb):

• Menu Presentation
  • VT9: 5
  • GST: 8
• Career Mode
  • VT9: 8 (has an edge because of the multi-tennis court games and multiple ways of training)
  • GST: 7 (assimilates the abilities of tennis legends)
• Consistently Follows Player's Motion
  • VT9: 8 (usually follows mostly but is more forgiving)
  • GST: 4 (character is mostly hitting ball off feet)
• Sounds / Music
  • VT9: 7
  • GST: 8
• Player's A.I. and A.I. Positioning
  • VT9: 8 (your character is erratic on an opponent's weak dropshots. Very noticeable when doing VT Coach)
  • GST: 1 (this is what makes GST frustrating)
• Player control with Nunchuk
  • VT9: 8 (works well with Nunchuk)
  • GST: 7 (still hits ball at feet whether you perform a backhand/forehand even when positioning character correctly)
• Online Play and Setup
  • VT9: 8
  • GST: 8
• Most realistic feel of tennis
  • VT9: 7 (very inconsistent recognition on forehand/backhand slicing)
  • GST: 3 (uses buttons in combination with swinging. Holding "A" button and swinging downward will still produce a lob)
• Overall Experience
  • VT9: 7
  • GST: 5

It seems like to me that those who favor one game over the other are disappointed by either Wii Motion Control, Player Placement, Online, etc. In terms of the better realistic feel for Tennis, I think Virtua Tennis has the edge mostly because their A.I. is much better, no use of buttons, forced calibration, and the wind-up animations trick the player into thinking it's full 1:1. GST has a much better lineup of players to select from but they are resorting to waggling in combination with buttons for lob and drop shot. Some people like this since they feel they have more control with the way strokes are done on the court but that defeats the purpose of WM+. GST also does not accomodate for wind-up. When you bring your WiiMote back for the swing, the game will take that as a swing. VT9 accomodates the wind-up by putting an animation in between hoping that the player will mimic that swing. As for online, my experience between both games were lagfree most of the time but in GST both you and the opponent will have to use Nunchuk to minimze the horrible A.I. not accomodating for wind-up. Some people are experiencing lag on both games and it would be wrong to judge based on lag since each match can differ depending where your opponent is located. Virtua Tennis 2009 does its best to mimic tennis movements. It does it pretty well but has trouble with slicing. Slicing is completely different from how it's mimicked in real life. VT9 also annoys you by continuously asking you to choose between Standard control and WiiMotionPlus even with WM+ plugged in.

Between both games, VT9 definitely has a deeper learning curve but the VT Coach helps with this (except for slicing - which is horrible). GST is much quicker to pick up since you can waggle the WiiMote but the Nunchuk is must. Also be prepared to play corner-to-corner rallies because that happens often no matter how well you time your swings. Both are still sequels away from creating true 1:1 motion of tennis but VT9 takes the edge mostly because it tries to make use of all the various swings with WiiMotion.

Detailed Review for VT9 to come soon