Peter, I too am an old tournament tennis player who turned to golf. I played with wood and was around when Wilson brought out the T2000. Our memories sometimes deceive us. On clay the rallies may have been longer. However technology has really changed that game as much or more than golf. The bigger, lighter and better balance rackets have aided returns more than serves. It is why the western grip, universally rejected afte Little Bill used it in the late teens and early 20's is now the grip of choice coupled with the 2 handed backhand. The mew rackets allow a western grip player to handle low balls, hit hem hard and with top spin. As a result, almost no one serves and volleys any more on hard courts and rarely on grass. There is less all court play then there was when Kramer was the best. It is because serve returns are harder and lower. So now most points are a collection of blasts from behind the baseline.As to who is the best, it is always difficult to compare eras. Federer is certainly in the upper echelons. Of those I saw in their primes, I think Laver could do the most for a very long time. Of course the money wasn't as good so there was a reason to stick around.
As to which is more strategic, the strategies are so different it is hard to say. In golf, one must plan in advance based on one's ability, the nature of the hole/course and the weather. Then, after every shot one must adjust the strategy to the result of the prior shot and the conditions. The opponent; the course , remains relatively static but the situation changes.
In tennis one must react to the opponent and the conditions and one must do so instantaneously. However, the skilled player has drilled incessantly on how to react to various shots. Thus faced with a cross court approach shot one usually responds down the line while the same shot where the opponent stays back will often result in a cross court return to take advantage of the lower part of the net. Recognizing the situation and responding with the appropriate shot is often the extent of the strategy unless the opponents particular strengths and weaknesses alter the planned responses. The best playeras either out-execute their opponents or upset these rote strategies with unconventional shots (think McEnroe).