Let me preface this by saying I have never tried the plus models. Having said that, the original 5:25 is such a great amp, I would personally save the extra $$$ and just get the older model.
That is, in fact, what I did -- I bought 2 of them, a 5:50 1x12 and a 5:25 1x10, for roughly $125 more than the price of one new Express 5:50+ 1x12.