Subclassing UITableViewCell correctly?

What is the difference between adding the subview to self and or to the content view?

Subview added to self

- (id)initWithFrame:(CGRect)frame { if ((self = [super initWithFrame:frame])) {
    UIImage *img = [UIImage imageNamed:@”lol.jpg”]; 
    UIImageView *imgView = [[UIImageView alloc] initWithImage:img]; 
    [self addSubview:imgView];
    [imgView release]; 
    return self;
}

Subview added to contentView

- (id)initWithFrame:(CGRect)frame { if ((self = [super initWithFrame:frame])) {
    UIImage *img = [UIImage imageNamed:@”lol.jpg”]; 
    UIImageView *imgView = [[UIImageView alloc] initWithImage:img]; 
    [self.contentView addSubview:imgView];
    [imgView release]; 
    return self;
}