Hi there. Very good question. Please note whenever you mention Markbass, people are going to come along and bash it even if they don't own the product. Ever since MB went to China.
I own a GK MB500 as my main amp and an MB200 for backup. The MB200 is twice the size as the Markbass and the Trace Elliot ELF. I don't have experience with either of these, so the best bet would be to get somewhere you can test them both out and see which one you like. I'm interested in the Trace Elliot because of the size and novelty. Although I've never owned a Markbass amp, I've always liked the sound of their combos. To me they're loud and punchy.
The original British made Trace Elliots have a great legacy and respect here on TB. But Peavey bought TE and the new ELF is made in China and I'm wondering if it will be true to the original Trace Elliot tone and reliability that they were known for.
Good luck, tough choices nowadays!