Yeah, sounds like you'd better run the cards with IPoIB instead of native Ethernet mode, else the switches won't talk to them.
For the speed difference, I kind of wonder if the SDP change toggled "connected mode" on.
An easy way to check is by doing an "ip addr" or "ifconfig" to show your ethernet/IPoIB settings.
If the adapters are not in connected mode, their mtu value will generally be around 2044 or similar (with mine anyway). When connected mode is enabled, the mtu shows up at about 65535 (ie 65k).
If that's what the difference turns out to be (no idea :>), then connected mode can be enabled "properly" by changing a setting in /etc/rdma/ ... something. Not remembering off the top of my head, but you should be able to find it pretty easily.