Should we use SPF (TXT) & SPF (type 99) or just one or the other?

Question

I was wondering, now our hosing provider supports SPF (type 99), weather or not to also use this type of record as well as the already in place SPF (TXT) record.

1. Is there any disadvantage of having both records set?
2. Should type 99 be formatted the same? e.g. "v=spf1 a mx ip4:xx.xxx.xxx.xxx ~all"

Thanks for any guidance!

Answer 1

Update: As written by Matt and Xavier (below) - RFC 4408 was obsoleted by RFC 7208, that says:

SPF records MUST be published as a DNS TXT (type 16) Resource Record (RR)

Regarding the original question: The SPF TXT record is sufficient.

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Post from Dec. 20,2012:

The SPF (type 99) dns resource record will be the successor of the SPF-TXT entry. According to this use both. Use SPF-RR with v=spf3 the SPF-TXT with v=spf1.

It is RECOMMENDED that a backward compatible TXT RR starting with v=spf1 be maintained

and

New software SHOULD look up TXT RRs if it finds no SPF RR, and MAY accept v=spf1 for backward compatibility.

and

Admins MUST NOT create RRs of type TXT that start with v=spf3.

Answer 2

According to the latest Proposed Standard (RFC 7208), you should use TXT records only:

3.1. DNS Resource Records

SPF records MUST be published as a DNS TXT (type 16) Resource Record (RR) [RFC1035] only. The character content of the record is encoded as [US-ASCII]. Use of alternative DNS RR types was supported in SPF's experimental phase but has been discontinued.