For me Martyn was individually superb in 03/04 when the team was pretty useless.
Performances at Anfield and Leeds spring to mind where he made numerous excellent saves where it felt like it was almost impossible to score against him.
In 04/05 he was part of a very organised defence and certainly played his part but I donít recall the same individual level of performance.
That was probably because the volume and quality of shots faced dropped significantly.
Towards the end his age was starting to show, errors in derby games, away at Anfield where it was clear that Gerrard could just roll it into the net, and at home when Cisse scored he so far over he was nearly in the Park End exposing the far post.
That was understandable as we saw with Howard, these errors happen as the senses start to fade.
Overall, I felt that he knew his own game very well. In that he very rarely left his line and basically left the defenders to deal with everything and then if it got through he would be in goal. It sounds simple but, in terms of top class (southall) performance levels, it did put pressure on the defensive performance or required top class individual shot stopping (which we saw in 03/04).
Re Howard, as @Shogun
says he too had one outstanding season, ironically this time it was when the team was playing really well. I suppose a huge red flag re Martinez should have been seen at the time...
Aside from that he was part of sideís that racked up clean sheets with good defensive performances (07/08 and 08/09 etc) but because we didnít finish 4th I think this went unheralded as much as Martynís performance in 04/05.
Obviously toward the end the decline was there for all to see.
Overall I think Martynís reputation for us is enhanced by the fact that he was only in the team for 2 seasons, one of which was the 4th season and that injury put an end to his decline rather than it being exposed time and again. I think the other factor was his career before us.
For Howard I think heís undervalued for the same/ opposite reasons. He was here years so the number of mistakes (always more memorable for keepers) adds up.
His good seasons didnít end up as good as the 4th in ďachievementĒ or miracle which also sticks in the mind.
And that he wasnít taken out of team when heíd gone, so he had a prolonged exposure to having fallen off a cliff.
But he was at least good for a relatively big number of seasons, whether individually or as part of good defences.
So for me, Howard edges it on that basis as the number of good performances, for us, is actually really high.