Maximum Wireless Performance
I found with the WNDR3700 that you have to run multiple streams to achieve its claimed 350 Mbps of "combined" wireless throughput. So I tried the same test with the 825 B1.
I set up a second notebook using a NETGEAR WNDA3100v2 client connected to the 5 GHz radio and my standard Intel 5300-equipped notebook connected to the 2.4 GHz radio and ran tests with multiple streams. Both clients were in the same room, within 10 feet of the router and both radios were set to Up to 300 Mbps (40 MHz channel bandwidth) mode.
As you may remember from the WNDR3700 review, the results for the 825 A1 were 187 Mbps of total downlink throughput (Figure 9) and 227 Mbps of aggregate uplink throughput (upstream plot).
Figure 9: D-Link DIR-825 [A1] aggregate wireless throughput - downlink
The B1 was much better than the A1 with a total of 225 Mbps downstream (Figure 10) and 267 Mbps up (upstream plot).
Figure 10: D-Link DIR-825 [B1] aggregate wireless throughput - downlink
For reference, the WNDR3700 yielded 252 Mbps total downstream and 262 Mbps upstream. So the B1's performance for wireless throughput using multiple streams is essentially the same as the WNDR3700 running upstream and within stiking distance downstream.
The natural question (already asked in the Forums) is why the DIR-825 B1 doesn't yield the same performance as the NETGEAR WNDR3700, given their similar hardware designs. I haven't done a design analysis beyond identifying the main devices used. But a glance at the two board photos in Figures 11 and 12 shows that while they may use the same key components, the hardware layouts are significantly different.
Figure 11: WNDR3700 board top - heatsink, RF shield removed
A key difference is the WNDR3700's use of on-board metamaterial antennas vs. the 825 B1's external dual-band dipoles. NETGEAR maintains that the metamaterial antennas provide some additional gain, which would help with wireless rate over range. And since each radio has its own set of antennas, the WNDR3700 doesn't have losses and other issues caused by the combiners in the 825 B1 that are necessary to feed the single dual-band antenna connection. On top of this, I'm sure that nuances and perhaps component differences in the radio designs also play a factor.
Figure 12: DIR-825 B1 board, shields removed
As for the difference in Routing throughput, that lies squarely in the code. So NETGEAR's code designers must have made tradeoffs that D-Link's didn't, which resulted in more oomph in routing speed.
And for the final "which one should I buy" question? Since both have way more routing throughput than anyone would need, I wouldn't let that be the deciding factor. But, in the end, I still think the edge goes to the WNDR3700. So pay the $50 extra and go your way rejoicing...