I think that either would work well. Both are high quality drivers, well made, from great companies.
The EV was designed more for PA than as a bass guitar driver. It handles more power than the Altec. As a sound reinforcement driver, I'd expect a flatter frequency response, but not by much. I've had a little experience with EV bass drivers, and it's all been good.
The Altec was, at one time, one of the most respected bass guitar drivers made. Some preferred JBL, some Altec, but those were the cream of what was available. I've never used Altecs, so I know them only by reputation.
That leaves the cabinet. Internal volume is probably about 3 ft^3 after subtracting the volume of the driver and port. I don't know what frequency it's tuned to. Both drivers are low Q drivers, and those tend to be rather forgiving with regard to cabinet size and tuning. Not knowing the tuning, I can't do a simulation I'd trust, but I wouldn't expect any frequency response extremes.
For myself, I'd probably go with the EV, based on personal experience, higher power handling and it being a newer driver. Unless the Altec were significantly less expensive, that is. But I'd like to hear what both of them sound like in the 115S.
http://www.electrovoice.com/downloadfile.php?f=DL15ST_Woofer_EDS.pdfhttp://www.greatplainsaudio.com/vintage_altec/421-8H_lfspkr_spec_sheet.pdf
