(The following comments are based on the first edition, which I bought a year ago. I see that Oxford published a second edition a few months ago.)
I have found P. H. Matthews' dictionary of linguistic terms to compare very favorably with David Crystal's A Dictionary of Linguistics and Phonetics. In spite of the considerable difference in size and price, I have found that Matthews' work has more of the terms I want to look up, and his explanations are often more to the point. I don't use it much for phonetic terminology, so any deficiency in this regard vis a vis Crystal has not been an issue for me.
I appreciate seeing the names of at least a few of the most outstanding linguists in history listed. New students in the field should find these references to the luminaries helpful. Their names show up in the literature with some regularity, and it is nice to have some place to turn for a quick summary of their contributions.
For students of linguistics, I recommend that you get Matthews' dictionary first, if you can't afford both at once, and then get Crystal's dictionary later. It is always helpful to have more than one reference of this sort on your shelf.