When it comes to golf games on the DS, you unfortunately aren't going to find any great ones. Your three best options are Tiger 05, Tiger 08 and True Swing Golf. As an owner of all three, I can tell you that True Swing Golf is the best game out of the three in terms of gameplay, mechanics, graphics, and physics. But it has its fair share of issues.
During standard gameplay, True Swing Golf is pretty good. You swing with your stylus, the power determined by swing speed and how far back you pull your backswing by dragging the stylus along the meter. You can opt to strike the ball at an angle for Draw or Fade but if you miss the ball entirely, it'll cost you a stroke. The ball's physics aren't what you'd call true to life, but they are as good as you're going to get on any DS golf game. The ball's flight feels free and not too clunky unlike with the DS Tiger games. Wind will affect the ball's flight and the bounce and roll of the ball are effected the the height of the terrain, thickness of the grass and whether or not the ground is wet. All the clubs behave accurately, although the Wedges have a quirky little feature in that they completely ignore the lie of the ball, so even if you're in heavy rough or the bunker, they act as if there's no problem. On a standard course you feel very in control, and if you're just doing a stroke or match play on the default courses then you'll enjoy a pretty solid golf experience that satisfies the need for portable golf.
Also, this game allows Single-Card Local Wifi play, so you only need one game cartridge to play with friends. Granted, Single-Card is limited to Match or Stroke play on just a few courses, and allows for only 9 holes at a time, and you can't select what character you want to be, merely male or female. But it's still nice to be able to play the basic game with just one card. Multi-Card play opens up your options for more courses, 18-hole games, and using your own character.
True Swing Golf's problems come in the career mode and when you upgrade your equipment. Starting with equipment, unlike other games that make things a little easier with better equipment, this game actually seems to make them harder. For example, upgrading your clubs to get better distance forces you to have to swing harder to get full power. So while you used to be about to swing at around 93 MPH to get full power, now you have to swing at about 114 MPH. Granted if you can do it you indeed enjoy more distance than with your old clubs, but it's harder to do and causes you to miss the ball entirely more often. Not only that, but the speed at which the game wants you to now hit the ball is faster than the DS is comfortable registering, so occasionally even if you indeed swing fast enough, you'll notice your club head's animation acting jerky and slow, resulting in a slow shot that's sure to fall short of its mark. Even worse, I've noticed it have a problem where the club will move slowly to the left at an angle long after you've stopped touching the screen, resulting in a slow, completely missed shot. I don't know if it's the game or just my DS's problem, but it's incredibly annoying when it happens.
The problem with career mode is that late into the game, the tournaments get ridiculously difficult. The wind is greatly exaggerated, forcing you to aim out of bounds sometimes just to keep the ball in play in the cross wind. Not only that but the holes are expanded in length while retaining the same par, so you'll find yourself playing Par 4 holes that require two full-power shots from the Driver just to have a prayer of getting to the green, or Par 5's that are 700 yards or more in length. You'll also notice that the CPU's scores in these tournaments is randomly generated, so while you're struggling to make par, the CPU will get an Eagle score on a 500 yard Par 4 in 25 MPH wind with a green surrounded in water. Since you don't actually see them play, it's easy for the game to just "assume" they got the Eagle. Challenging is one thing, but this just gets absurd. And since you have to win tournaments to unlock courses into free play, you'll likely miss out on a lot of the later ones. Ironically, you probably wouldn't want to play them for fun, anyway.
So while I do like True Swing Golf and play it pretty often when I want to golf in bed, the various frustrations that come with it keep it far from being perfect. If you stick to stroke play on the beginner to intermediate courses it's a fun little golf game, but you'd best have a thick skin if you're going to try to conquer Championship Mode or upgrade your equipment. I would only recommend it to serious video golf fans, the casual player would probably not have the patience for it.