I own a dual analog meter, a birdog, and have on permenent loan, a satlook NIT. all work indipendant of the ird (battery pack), which is often very handy.
dual analog meters are great for field work, they have alot of really usefull debuging abilities. dual meters are nice if your doing any dish500 installs or torodial installs as you can aim the two outside lnb's at the same time. for adjusting skew. also if you turn them off and slave them to an ird the meter will tell you the voltage the ird is sending, this helps determine voltage drop issues, you can also tell the current draw, this helps determine funny things like pinched or stapled coax, water corrosion, etc. they also show you if the 22kz is present or not, handy for starchoice lnb's and others.
the birdog is handy for quick and acurate installs, people often say they identify the satellite their on, not really though, it tells you signal strength and if and only if your on the satellite your birdog is set to then it will show you pq or ber, the ber is pretty acurate and you can really fine tune a dish. birdog can not control 22khz though, but it can control diseqc switchs. its limited though by what birdog.tv thinks the sat looks like, so if your birdog is not 100% current then you might be on the right sat, but it wont lock. you have not control over the tp, you just have to hope birdog.tv is picking an active one. it has no diagnostic abilities at all. birdog also only works with dvb, no analog or dgII locking.
the satlook nit is the cats a** its amazing. it can control 22khz, disrwc, even a diseqc v1.2 motor ! it shows you the entire spectrum of what its seeing, it lets you take pictures of the sats you like so you can easily identify them later on another install. its handy too becayse you can overlay a known satellite and instantly see new tps pop up from wildfeeds. it lets you move the marker over the tp and it will even do its best to determin the name of the channel on that tp, the symbol rate and fec as well. it has an analog tuner built in as well.
because you can see the entire spectrum you can acuratly tweak your skew on linear, as you can see the V tps starting to pop up out of the noise floor when you skew the H to far.
when youve got two satellites close together you can also see how the two are bleeding into each other if your dish is too small (smaller dish larger the focal point, larger dish the better isolation between satellites) sometimes you may have great signal, but if there is another satelllite close by using the same tp your quality may be low because the other satellite is bleeding in, spectrum analyzers are the only way to determine this accuratly.