Guetermann Mara 100 is the same as their SewAll. Mara 30 = Top Stitch and Mara 70 = Extra Strong. Mara 120 and Mara 150 are finer than SewAll, better suited to overlocking or very fine fabrics.
http://www.williamgee.co.uk/product-category/sewing-threads/gutermann-sewing-threads/page/2/Other good brands are Superior Threads, Madeira, Mettler, DMC and Presencia.
A lot of people say they use Coats Moon without problem, but it is thicker than Guetermann SewAll which a lot of us take as the 'standard' for ordinary sewing machine use, and also when you look closely at Moon it is hairy and that's not good.
@Lowena when you say your machine doesn't like Guetermann, did you use SewAll polyester or Guetermann cotton 50? If your machine is fine-tuned for cotton thread and then you switch to polyester (any brand) you might need to tweek the tenson settings. Before the advent of stretchy fabrics and thus the need for the slightly stretchy polyester threads everyone used cotton (usually Coats Sylko) in their machines and they probably had fewer tension problems than we do now with the plethora of thread which is around.